Apparatuses, systems, and methods for improved performance of a pressurized system

ABSTRACT

A system, apparatus, and method for improving performance of a pressurized system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. provisional patentapplication Ser. No. 61/143,947, filed Jan. 12, 2009, which isincorporated herein in its entirety and is currently pending and thepresent application is a continuation-in-part of U.S. patent applicationSer. No. 12/189,630, filed Aug. 11, 2008, which is incorporated hereinin its entirety and is currently pending.

FIELD OF THE INVENTION

The present invention is concerned with reducing pulsations in fluidsystems.

Embodiments of the invention also increase fluid flow, reduces powerconsumption, or both over traditional systems, resulting in smoother,more efficient fluid flow in a closed system.

BACKGROUND OF THE INVENTION

The theory of cyclical finite amplitude pressure wave propagation inpipes is discussed, for example, in Professor Gordon P. Blair's book“Design and Simulation of Two-Stroke Engines” and will not be repeatedin detail in this application. Rather, the following is a summary ofsome of the underlying principals of physics that this inventionexploits:

-   -   1. There are always two waves propagating in opposite directions        within a pipe that has flow.    -   2. The convention is to call one wave the right wave and the        other wave the left wave.    -   3. The two waves superimpose upon each other and create the        pressure that can be measured by a pressure transducer.    -   4. It is not possible to measure the right or left wave        separately, however they can be tracked, for example, by a        one-dimensional gas flow simulation software developed by        OPTIMUM Power Technology.    -   5. Both waves propagate without reflection if the cross        sectional area of the pipe stays the same.    -   6. When the cross sectional area of the pipe changes, part of        the wave continues to propagate and the remainder of the wave        reflects in the opposite direction.    -   7. When pipes branch or terminate, part of the wave continues to        propagate and the remainder of the wave reflects in the opposite        direction.

As a result of these phenomena, a compressor creates pulsations thatpropagate away from it and piping that attaches to both the suction anddischarge sides of the compressor create pulsations that propagate backto the compressor, affecting compressor performance.

By properly phasing the cylinders of the compressor and/or properlychoosing the lengths and diameters of pipes in fluid communication withthe compressor, outward bound pulsations can be attenuated and inwardbound pulsations can used to improve the performance of the compressor.

A fluid, whether gaseous or liquid, may flow through a conduit or duct.The fluid may be propelled by a pressure creating device, such as acompressor or other type of pump. One type of compressor used to propelfluid, particularly gas, is a reciprocating compressor. The pressure andflow delivered by reciprocating compressors varies throughout the strokeof each compressor cylinder piston, thus creating pressure waves orpulses that propagate at acoustic velocity throughout the attachedpiping system. Effective control of the pressure pulsations generated byreciprocating compressors is desirable for various reasons, including toprevent damaging forces and stresses in system piping, vessels, andmechanical equipment and structures, and to prevent detrimentaltime-variant suction and discharge pressures at or near the compressorcylinder flanges.

A reciprocating compressor may have a piston that is moved alternatelytoward one end of a cylinder and then to an opposing end of the cylinderand fluid may be propelled from the cylinder by the piston in either oneor both directions of piston movement. A piston that propels fluid whenmoving in only one direction may be referred to as single-acting piston,while a piston that propels fluid when moving in both directions may bereferred to as a double-acting piston. Double-acting pistons compressgas at the discharge of the compressor using both strokes of the piston,while single acting pistons compress gas at the discharge of thecompressor using only one stroke of the piston. Exemplary double-actingcompressors are those manufactured by Ariel Corporation of Mount Vernon,Ohio.

The pumping action of each single-acting or double-acting piston createscomplex cyclic pressure waves. The pressure waves of a double-actingpiston generally have a primary frequency at twice the compressoroperating speed with many harmonics. Variations in pressure withinconduits and ducts created by such pumping actions are commonly referredto as pulsations.

In a typical fluid pumping system (e.g., a natural gas pumping station),wherein the pumping is performed by one or more reciprocatingcompressors, pressure pulsations are controlled with a system of primaryand/or secondary volume bottles, often with complex internal choketubes, baffles, and chambers, as well as various orifice platesinstalled at various locations in the system piping. Those pressurepulsation control devices are thought to accomplish pulsation control byadding resistance, or damping, to the system, and their use results inpressure losses that typically exist both upstream (or in a directionaway from the compressor cylinders) and downstream (or in a directiontoward the compressor cylinders) of the compressor cylinders. For commonpipeline transmission applications, particularly those having lowpressure ratios between their inlets and outlets, such as natural gaspipeline systems, pressure losses can noticeably degrade systemoperating efficiency. As larger high-speed compressors have beenincreasingly applied to pipeline transmission applications, theinfluences of existing pressure wave or pulsation control devices arethought to have become more detrimental to performance, because of thehigher frequency pulsations that must be damped in such high-speedcompressors. In certain cases, installed systems using traditionalmethods of pulsation control have been reported to add 20 percent ormore to the driver horsepower requirements for high-speed, low-ratiocompressors.

Commonly, in systems such as natural gas pipeline systems, bottles areemployed near the outlets of their compressors to dampen pulsationsclose to the fluid source. In addition to the drawbacks of using bottlesto control pulsation as described above, bottles are commonly verybulky. A natural gas pipeline or other system that eliminated,decreased, or did not rely exclusively on bottles to address pulsationmay overcome certain drawbacks. Thus, a natural gas pipeline or othersystem that addressed pulsation by attenuating pulses at variouspositions along the pipeline without significantly affecting efficiencyof the system may be desirable.

Study has been made as to the effect of the use of differing lengthparallel tubes to cancel sounds of a particular wavelength. Acousticwave interference in pipes was studied in 1833 by Herschel, whopredicted that sound could be canceled by dividing two waves from thesame source and recombining them out of phase after they followed pathsof different lengths. Experiments by Quincke in 1866 verified thatHerschel's system did suppress sound.

Variations on the Herschel-Quincke solutions have been proposedincluding a method for controlling exhaust noise from an internalcombustion engine by using bypass pipes such as shown in U.S. Pat. No.6,633,646 to Hwang (hereinafter “Hwang”). See FIG. 1 and FIG. 5 ofHwang. In such an apparatus, a main exhaust pipe is provided with twoU-shaped bypass pipes through which the exhaust passage of the main pipeis partially diverted before being reintegrated. With such aconstruction, the phase difference between the main noise components ofthe exhaust gas passing through the fixed pipe and the noise componentsof the exhaust gas passing through the first bypass pipe is adjusted 180degrees, thus suppressing the main noise component and its oddharmonics. The length of the second bypass pipe is adjusted so that thenoise component having a frequency of two times the frequency of themain noise component is suppressed. However, the above method does noteffectively attenuate the 4th harmonic, i.e., the noise component havinga frequency four times the main noise component, nor any other harmonicsdivisible by 4. Such an arrangement furthermore operates on a singleprimary frequency and certain of its harmonics and so is unlikely toprovide effective noise attenuation over a range of noise frequencies.Furthermore, Herschel, Quincke, and Hwang directed their efforts towardsound attenuation, not improvement of system integrity and performance.While attenuation of sound and pulsations may be achieved by similarmeans, they operate differently by degrees to achieve different results.For example, reduction of sound is frequently directed to human comfortand reduction of high frequency wavelengths that are bothersome to humanbeings. Conversely, pulsation reduction frequently focuses on reducinglow frequency wavelengths that may cause damage to mechanical systems,such as pipes, conduits, ducts, mechanical equipment and structures,sometimes in critical safety applications such as natural gas pipelines.

U.S. Pat. No. 5,762,479 to Baars et al. (hereinafter “Baars”) isdirected to a discharge arrangement for a reciprocating hermeticcompressor of the type used in small refrigeration systems. Thatarrangement includes a gas discharge tube through which gas flows from agas discharge chamber. To attenuate a pulse at a certain frequency, partof the gas flow from the gas discharge chamber is displaced through agas discharge auxiliary tube. The lengths of the gas discharge tube andgas discharge auxiliary tube differ by a fraction, preferably half, ofthe length of a wave at that frequency. As such, when the gas flow inthe gas discharge tube and gas discharge auxiliary tube join, the pulseis attenuated.

Baars does not, however, address system performance such as gas flowrate or efficiency. Additionally, Baars only addresses attenuation of apulse at a single frequency, and does not attenuate pulses at any otherfundamental or harmonic frequencies. Additionally, there may be a needfor a pulsation attenuation apparatus, system, and method thatattenuates pulses at multiple frequencies and, unlike Baars, is directedto natural gas pipeline systems.

U.S. Pat. No. 3,820,921 to Thayer (hereinafter “Thayer”) is directed toa hermetic refrigerator compressor with radially-configured cylinders.Thayer discloses a six-cylinder discharge arrangement in which the firstthree cylinders have discharge tubes that connect side-by-side at ajoint to one common discharge line, and the other three cylinders havedischarge tubes that connect side-by-side at a joint to a second commondischarge line. The discharge tubes may be of unequal length to reducenoise including that caused by vibration and resonance at certainfrequencies. That configuration may minimize the need for mufflers, andmay increase compressor efficiency. The side-by-side relationship at theconnection point at the joint is said to create an aspiration effect inthe joint by which gas being discharged from one of the cylinders helpsto withdraw the discharge pulses from the opposing cylinder.

Thayer is directed to noise reduction in a hermetic refrigeratorcompressor with radially-configured cylinders and does not go toimproving performance of a compressor with in-line cylinders, such asthose sometimes used in natural gas pumping. Thayer is further directedto an apparatus having a single joint in which flows are combined andarranged to create an aspiration effect, not a system that combinesflows at two or more locations in series to improve compressorperformance by attenuating various pressure variations. Accordingly,there may be a need for a pulsation attenuation that improves theperformance of a compressor in a system such as a natural gas system.

Furthermore, the Thayer system does not recognize the wave reflectionissue created by its joint. At discontinuities in the pipe flowconditions and geometry, such as at junctions of multiple routes offluid flow and with respect to diameter changes, wave reflectionnormally occurs. Where the discontinuity is introduced close to theoutlet of a compressor, such as in Thayer, the reflected portion of awave may significantly affect the pressure at the outlet of thecompressor. Thayer fails to address that issue. Additionally, there maybe a need for a pulsation attenuation apparatus, system, and method thataddresses that issue and further is, unlike the hermetic refrigeratorcompressor in Thayer, directed to natural gas pipeline systems.

Thus, certain embodiments of the present pulsation attenuationapparatuses, systems, and methods may account for those reflectedportions of waves when determining, e.g., pipe length and positioning ofcertain junctions. Other embodiments of the present pulsationattenuation systems, apparatuses, and methods may account for thosereflected portions of waves propagating through natural gas pipelines.

Embodiments of the present pulsation attenuation apparatuses, systems,and methods including reciprocating compressors with multiple sources,such as multiple cylinders, may reduce the pressure wave propagatingthrough the fluid when combined from the multiplicity of sources whileemploying other means to improve system performance.

Certain embodiments of the present apparatuses, systems, and methods forimproved performance of a pressurized system attenuate pulsations in aconduit or duct. While sound wave propagation cancellation and pulsepropagation cancellation may be based on some of the same principles, itshould be recognized by one skilled in the art of wave dynamics thatreduction of sound wave propagation has a different goal and operatesdifferently from reduction of pulse propagation to improve performanceof a pumping system.

Certain embodiments of the present apparatuses, systems, and methods forimproved performance of a pressurized system may further preserve theintegrity of piping and vessel systems subjected to pulsations.

Embodiments of the apparatuses, systems, and methods for improvedperformance of a pressurized system described herein reduce pulsationsin pumping systems, including pumping systems utilizing reciprocatingcompressors and rotary pumps (collectively referred to herein as“pumps”).

Embodiments of the present apparatuses, systems, and methods forimproved performance of a pressurized system described herein reduceenergy consumption as compared with existing systems.

Embodiments of the present apparatuses, systems, and methods forimproved performance of a pressurized system described herein increaseflow in pumping systems as compared to existing systems.

Embodiments of the present apparatuses, systems, and methods forimproved performance of a pressurized system described herein reduce thepressure differential against which pumps operate as compared toexisting systems.

Embodiments of the apparatuses, systems, and methods for improvedperformance of a pressurized system described herein may employ multiplemeans to reduce or cancel primary and harmonic frequencies of wavespropagating through the pumped fluids, such as natural gas, and mayimprove system performance such as flow rate or efficiency.

SUMMARY OF THE INVENTION

Embodiments of apparatuses, systems, and methods for improvedperformance of a pressurized system are directed to systems, methods andapparatuses for reducing pressure waves in a fluid pumping system and tosystems, methods and apparatuses for increasing flow or efficiency in afluid pumping system.

In accordance with one embodiment of the present invention, a naturalgas pumping system is provided. The natural gas pumping system includesa reciprocating compressor with two cylinders where each cylinder has aninlet through which natural gas is received and an outlet through whichnatural gas is discharged. The natural gas pumping system furtherincludes a first conduit having a first end in fluid communication withthe outlet of the first cylinder and a second end in fluid communicationwith a junction and a second conduit having a first end in fluidcommunication with the outlet of the second cylinder and a second end influid communication with the junction.

In accordance with another embodiment of the present invention, anatural gas pumping system that includes a reciprocating compressor isprovided. The reciprocating compressor includes a first cylinder havingan inlet through which natural gas is received and an outlet throughwhich natural gas is discharged and a second cylinder having an inletthrough which natural gas is received and an outlet through whichnatural gas is discharged. The natural gas compressor also includes afirst conduit having a first end in fluid communication with the inletof the first cylinder and a second end in fluid communication with ajunction and a second conduit having a first end in fluid communicationwith the inlet of the second cylinder and a second end in fluidcommunication with the junction.

A pressure wave attenuation system is provided in another embodiment ofthe present invention. The pressure wave attenuation system includes oneor more reciprocating compressors together comprising a first cylinder,a second cylinder, and a third cylinder, a first header coupled to thefirst cylinder and a first junction, a second header coupled to thesecond cylinder and the first junction such that a pressure wavepropagating in the fluid flowing through the first header is out ofphase with fluid flowing through the second header when the fluidflowing from the first and second headers combine at the first junction,a third header coupled to the third cylinder and a second junction; anda first branch line extending from the first junction to the secondjunction.

In yet another embodiment, a pressure wave attenuation system isprovided that includes one or more reciprocating compressors togethercomprising a first cylinder, a second cylinder, a third cylinder, and afourth cylinder; a first header in fluid communication with the firstcylinder and a first junction; a second header in fluid communicationwith the second cylinder and the first junction such that a pressurewave propagating in the fluid flowing through the first header and apressure wave propagating in the fluid flowing through the second headerare attenuated when the fluid flowing from the first header and thefluid flowing through the second header combine at the first junction; athird header in fluid communication with the third cylinder and a secondjunction; a fourth header in fluid communication with the fourthcylinder and the second junction such that a pressure wave propagatingin the fluid flowing through the third header and a pressure wavepropagating in the fluid flowing through the fourth header areattenuated when the fluid flowing from the third header and the fluidflowing through the fourth header combine at the second junction; afirst branch line in fluid communication with the first junction and athird junction; and a second branch line in fluid communication with thesecond junction and the third junction, the length of the second branchline differing from the length of the first branch line such that apressure wave propagating in the fluid in the first branch line and apressure wave propagating in the fluid in the second branch line areattenuated when the fluid flows from the first and second branch linescombine at the third junction.

In another embodiment, a method of reducing pressure variations in anatural gas pumping system is provided. That method includes combiningnatural gas flowing from a first reciprocating cylinder having a firstperiodic pressure fluctuation characteristic operating in a first phasewith natural gas flowing from a second reciprocating cylinder having asecond periodic pressure fluctuation characteristic operating in asecond phase when the first periodic pressure fluctuation characteristicis out of phase with the second periodic pressure fluctuationcharacteristic.

The present invention also includes a method of attenuating pressurewaves in a natural gas pumping system, comprising combining gas flowingfrom a first cylinder in which propagates a first periodic wave with gasflowing from a second cylinder in which propagates a second periodicwave such that the first periodic wave and the second periodic wave areout of phase.

Accordingly, the present invention provides solutions to theshortcomings of prior fluid pumping systems, apparatuses, and methods.Those of ordinary skill in the art will readily appreciate, therefore,that those and other details, features, and advantages of the presentinvention will become further apparent in the following detaileddescription of the preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, include one or more embodiments of theinvention, and together with a general description given above and adetailed description given below, serve to disclose principles ofembodiments of pulsation attenuation devices and networks.

FIG. 1 illustrates an embodiment of a pulsation attenuation device;

FIG. 2 illustrates a schematic diagram of an embodiment of a sixcylinder reciprocating compressor type pump;

FIG. 3 illustrates a schematic diagram of an embodiment of a sixcylinder reciprocating compressor type pump;

FIG. 4 illustrates an embodiment of a fluid pumping system;

FIG. 5 illustrates an embodiment of an inlet piping system;

FIG. 6 illustrates an embodiment of a six-cylinder reciprocatingcompressor type pump system.

FIG. 7 illustrates an embodiment of a tuned loop network including twotuned loops;

FIG. 8 illustrates an embodiment of a tuned loop network including twotuned loops respectively in fluid communication with the inlet andoutlet of a pump;

FIG. 9 illustrates an embodiment of a network including a suction tunedloop network and a discharge tuned loop network;

FIG. 10 is a flow chart of an embodiment of a method for attenuatingpulsations, vibrations, or other undesirable waves in a fluid;

FIG. 11 is a flow chart of an embodiment of a method of attenuatingpressure waves or pulsations created by a pump; and

FIG. 12 illustrates an embodiment of a fluid pumping system employingaspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to embodiments of apparatuses, systems, andmethods for improved performance of a pressurized system, examples ofwhich are illustrated in the accompanying drawings. Details, features,and advantages of those apparatuses, systems, and methods for improvedperformance of a pressurized system will become further apparent in thefollowing detailed description of embodiments thereof. It is to beunderstood that the figures and descriptions included herein illustrateand describe elements that are of particular relevance to apparatuses,systems, and methods for improved performance of a pressurized system,while eliminating, for purposes of clarity, other elements found intypical fluid pumping systems.

Any reference in the specification to “one embodiment,” “a certainembodiment,” or any other reference to an embodiment is intended toindicate that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment and may be utilized in other embodiments as well. Moreover,the appearances of such terms in various places in the specification arenot necessarily all referring to the same embodiment. References to “or”are furthermore intended as inclusive so “or” may indicate one oranother of the ored terms or more than one ored term.

FIG. 1 illustrates an embodiment of a pressure wave attenuation device100, also referred to as a pulsation attenuation device, having onetuned loop 102. The tuned loop 102 includes an inlet conduit 104 coupledto an inlet junction 106. The inlet junction 106 has an inlet 108coupled to the inlet conduit 104, a first outlet 110 and a second outlet112. The first outlet 110 of the inlet junction 106 is coupled to afirst end 114 of a first branch line 116, also referred to as a firstattenuating conduit, and the second outlet 112 of the inlet junction 106is coupled to a first end 120 of a second branch line 122, also referredto as a second attenuating conduit.

The inlet conduit 104 illustrated in FIG. 1 is a pipe having a length,an internal diameter, and an internal area. Similarly, the first branchline 116 and the second branch line 122 illustrated in FIG. 1 are pipesand each has a length, an internal diameter, and an internal area. Otherconduits discussed herein may have various shapes (e.g., round orrectangular), but those conduits generally also have a length and aninternal area. The dimensions (e.g., length and area) of those conduits(e.g., 104, 116, and 122) furthermore affect various aspects of systemoperation as discussed herein.

It should be noted that the term “junction” as used herein includes anyconnecting device to which three or more conduits may be coupled,including, for example, a wye-, a tee- or an x-shaped junction, or ajunction formed on or with a conduit. In an embodiment, the inletjunction, outlet junction, first branch line, and second branch line areformed as a single entity. In another embodiment, the inlet junction,outlet junction, first branch line, and second branch line are formed ofmore than one component wherein at least one junction is formed with atleast one branch line.

In certain embodiments, the branch lines and attenuating conduits 116and 122 are formed straight, angled, curved, or otherwise to meet thedesires or constraints of an application, such as to minimize the sizeof the pulsation attenuation device 100.

An outlet junction 124 includes a first inlet 126 coupled to a secondend 118 of the first attenuating conduit 116 and a second inlet 134coupled to a second end 128 of the second attenuating conduit 122. Theoutlet junction 124 also has an outlet 130, which may be coupled to anoutlet conduit 132 as illustrated in the embodiment shown in FIG. 1.

The pulsation attenuation device 100 may carry a pressurized fluid, suchas, for example, natural gas. The inlet conduit 104 may be arranged influid communication with a pump, such as for example the pump 450illustrated in FIG. 4, pump 806 illustrated in FIG. 8, or pump 906illustrated in FIG. 9, applying pressure to the fluid. The outletconduit 132 may be in fluid communication with a system (not shown) towhich the pressurized fluid is carried. Fluid communication with eitherthe pump (e.g., 450, 806, 906) or the system may, for example, beaccomplished by direct coupling or through additional conduits. Thetuned loop 102 may attenuate pressure fluctuations, variations, or wavesin a primary pressure wavelength propagated in the fluid and oddharmonics of that primary pressure wavelength.

The term “pressure wave” as used herein describes a periodic, repeatingvariation or fluctuation in pressure. The term “pulsation” as usedherein refers to the difference between a highest pressure point orportion of the pressure wave and the lowest pressure point of portion ina periodic pressure wave. The term “peak pressure” generally refers tothe higher pressure portion of the periodic pressure wave, but may alsorefer to the lower pressure portion of the periodic pressure wave. Thepressure wave may repeat for any length of time. In a reciprocatingcompressor example, the pressure wave will generally repeat periodicallyat a frequency that is constant while the reciprocating compressoroperates at a constant speed. When the speed of the reciprocatingcompressor changes, the frequency of the periodic pressure wavegenerally changes to a different frequency.

Regarding conduit sizes, the inlet conduit 104 and the outlet conduit132 may have approximately the same cross-sectional area. The firstattenuating conduit 116 may have approximately half the cross-sectionalarea of the inlet conduit 104 and the outlet conduit 132, and the secondattenuating conduit 122 may have approximately half the cross-sectionalarea of the inlet conduit 104 and the outlet conduit 132. For example,where a fourteen inch, schedule 80, round, steel inlet conduit 104 and afourteen inch, schedule 80, round, steel outlet conduit 132 havingcross-sectional areas of 122.72 square inches are used, the first andsecond attenuating conduits 116 and 122 may be ten inch, schedule 80,round, steel conduits having cross-sectional areas of 71.84 squareinches each.

Dividing fluid flow into different length conduits of appropriatelengths and areas, and then recombining those flows may reduce or cancelcertain pressure waves emanating from a pump (such as pump 450, 806, or906) thereby smoothing the pressure of the fluid flow leaving thepulsation attenuation device 100. For example, where one or moreproperly designed tuned loops 102, 802, 910, and 912 are locateddownstream of the discharge of a pump, such as pump 806 shown in FIG. 8or pump 906 shown in FIG. 9, certain pressure waves in the fluid flowingdownstream of the tuned loop 102, 802, 910, and 912 should beattenuated.

Locating a tuned loop 102 or an inlet junction 106 of a tuned loop 102at an optimum location with respect to a pump (e.g., 450, 550, 694, 806,and 906) can partially reflect waves or pulsations so as to increaseflow or increase pump (e.g., 450, 550, 694, 806, and 906) efficiency.For example, where a properly designed tuned loop 102 is located at anappropriate location downstream of a pump (e.g., 450, 550, 694, 806, and906) waves partially reflected upstream may have a phase relationshipwith cylinder cycles (not shown in FIGS. 8 and 9) of the pump (e.g., 806and 906) reducing pressure at the pump (e.g., 450, 550, 694, 806, and906) cylinder outlets discharge (e.g., near the pump outlet 808 and 908as shown in FIGS. 8 and 9). That phase relationship may determine, atleast in part, the flow capacity and efficiency and can be varied by,for example, varying the lengths of the first branch 116 and secondbranch 122 of the tuned loop 102.

Thus, while previous fluid pumping systems dissipated a significantamount of energy by various apparatuses and methods including use ofbottles and by muffling fluid flow, embodiments of pressure wave andpulsation attenuation cancel or reduce undesirable pressure waves andpulses, thereby dissipating less energy than muffling. Furthermore,embodiments of pressure wave and pulsation attenuation improve pump(e.g., 450, 806, and 906) efficiency or system flow capacity byaddressing reflected waves at the cylinder outlets (e.g. 441, 442, 443,and 444 for pump 450, near the outlets 808 and 908 for pumps 806 and906). Embodiments of pressure wave and pulsation attenuation may improvepressure conditions at a pump inlet (e.g., 804 and 904 as shown in FIGS.8 and 9) as well.

The pulsation attenuation devices, networks, and methods describedherein are based in part on the following principles:

-   -   1) Repeating pulses with frequency F and period P are made up of        the sum of a series of sine waves with frequencies F, 2*F, 3*F,        . . . periods P/1, P/2, P/3, . . . and amplitudes A1, A2, A3, .        . . . These sine waves may be referred to as the primary        frequency, F, the first harmonic frequency, 2*F, second harmonic        frequency, 3*F, and so on. This infinite series of sine waves        may be referred to as a Fourier series.    -   2) The sum of two sine waves of equal amplitude but 180 degrees        out of phase is zero (i.e. the waves cancel each other        [sin(X+180 deg)=−sin(X)]).    -   3) A pressure wave propagating down a pipe can be divided into        two roughly equal parts with a Y branch.    -   4) If the two divided pressure waves travel different distances        and are recombined at a later point, the different distances        will time shift and may phase shift, the two pressure wave        parts.    -   5) The time/phase shift caused by such a separation and        recombination will cancel frequency components that have periods        of 2, 6, 10, 14, . . . times the time shift if they are present        in the repeating pressure wave.    -   6) The delay loop created by dividing pressure waves, causing        the pressure waves to travel different distances, and        recombining the pressure waves should also attenuate, that is        partially cancel, frequencies components of the pulse in between        the canceled frequencies except for the frequencies that are        half way between two consecutive canceled frequencies.    -   7) The difference in length of two paths of different distances        can be “tuned” to one or more frequencies present in a pressure        wave to dramatically reduce the pressure waves in a conduit or        duct.    -   8) If the lengths of the two paths are tuned to the speed at        which a pump is running, the pressure waves will generally be        substantially reduced without a significant pressure loss.

FIG. 2 illustrates a schematic diagram depicting a six cylinderreciprocating compressor 200 type pump. The reciprocating compressor 200includes a motor 202 that turns a crankshaft 204. The reciprocatingcompressor 200 may be of any desired type, including an electricallypowered or natural gas powered compressor 200.

The crankshaft 204 illustrated in FIG. 2 is coupled to a firstconnecting rod 210, a second connecting rod 212, a third connecting rod214, a fourth connecting rod 216, a fifth connecting rod 218, and asixth connecting rod 220. In various embodiments, the crankshaft 204 maybe coupled to any number of connecting rods or other piston operatingapparatuses.

The first connecting rod 210 is coupled to a first piston 230 in a firstcylinder 250. The second connecting rod 212 is coupled to a secondpiston 232 in a second cylinder 252. The third connecting rod 214 iscoupled to a third piston 234 in a third cylinder 254. The fourthconnecting rod 216 is coupled to a fourth piston 236 in a fourthcylinder 256. The fifth connecting rod 218 is coupled to a fifth piston238 in a fifth cylinder 258. The sixth connecting rod 220 is coupled toa sixth piston 240 in a sixth cylinder 260.

For simplicity, FIG. 2 shows a single simplified disc-like crank throw222, 224, and 226 for each pair of opposed cylinders 250 and 256, 252and 258, and 254 and 260. Alternatively, the crank shaft 204 may have anindividual crank throw for each cylinder 250, 256, 252, 258, 254, and260 or any other crankshaft 204 configuration desired.

The frequency of the reciprocating compressor 200 is the frequency atwhich the reciprocating compressor 200 applies its propelling force. Forexample, FIG. 2 illustrates a double acting reciprocating compressor 200with double acting cylinders 250, 252, 254, 256, 258, and 260. Thepistons 230, 232, 234, 236, 238, and 240 of those cylinders 250, 252,254, 256, 258, and 260 propel fluid with each motion in both directionsin a cylinder 250, 252, 254, 256, 258, and 260. Thus, the frequency ofthe pressure waves or pulsations for each of the cylinders 250, 252,254, 256, 258, and 260 will be twice the frequency of the rotating speedof the compressor (one pulsation or high pressure peak for each motionof the cylinders 250, 252, 254, 256, 258, and 260 during each cycle ofthe motor 202).

A wavelength, for purposes of an embodiment, is the period of thepressure wave times the acoustic velocity of the fluid in which thepressure wave is propagating. Thus, in the embodiment of FIG. 2, whereinfluid is being pumped by the reciprocating compressor 200, the primarywavelength of a pressure wave for one cylinder 250, 252, 254, 256, 258,and 260 is the period from one fluid propelling motion of the cylinder250, 252, 254, 256, 258, and 260 to the next fluid propelling motion ofthe cylinder 250, 252, 254, 256, 258, and 260 multiplied by the acousticvelocity of the fluid.

Pumps (e.g., 200, 450, 806, and 906) furthermore frequently operate atvarious speeds. The ratio of the fastest speed to the slowest speed ofoperation in pumping system embodiments may be a narrow, but significantrange, such as a 25% turndown rate. Moreover, in a natural gas pumpingstation, the pump (e.g., 200, 450, 806, and 906) speed may vary to meeta varying demand on the gas pumping system. A primary wavelength may,therefore, be established for the pump (e.g., 200, 450, 806, and 906) ata selected speed. The primary wavelength, however, will vary when thespeed of the pump (e.g., 200, 450, 806, and 906) is varied. Accordingly,embodiments of the present pressure wave attenuation apparatuses,systems, networks, and methods operate to minimize pressure wavescreated by the pump (e.g., 200, 450, 806, and 906) operating over arange of speeds.

Different speed and load conditions under which the pump (e.g., 200,450, 806, and 906) operates may create different repeating pressurewaves and different Fourier series. Embodiments of pulsation attenuationuse one or more tuned loops or other systems, apparatuses, or methodsdescribed herein to effectively attenuate the critical frequenciespresent in the Fourier series that characterize the speed and load rangeof the pump (e.g., 200, 450, 806, and 906).

It should be recognized that, in embodiments, full cancellation mayoccur for sinusoidal pressure waves when the fluid stream carrying thosesinusoidal pressure waves is divided into equal parts and recombined at180 degrees out of phase. For sinusoidal pressure waves that arerecombined at a relative phase shift of 360 degrees, effectively nocancellation may occur and for sinusoidal pressure waves that arerecombined at other degrees out of phase, partial cancellation of thosesinusoidal pressure waves may occur. A tuned loop 102, also referred toas a delay loop herein, and other flow combining systems, apparatuses,and methods described herein, may thus cancel a series of pressure wavefrequency components propagating in a fluid (i.e., a primary frequencyand its odd harmonics) and provide partial cancellation or attenuationof one or more ranges of pressure wave frequencies, while leavingcertain pressure wave frequencies, such as even frequencies divisible byfour, not effectively attenuated.

In certain embodiments where pressure wave attenuation is desired in apumped fluid, it may be less necessary, or simply unnecessary, toattenuate higher harmonics. Higher harmonics tend to be lower amplitudein certain fluid flow applications and so those higher harmonics may notbe as important to attenuate, or may create pressure waves that are notnecessary to attenuate.

Referring again to FIG. 1, in pressure wave attenuation, a first tunedloop 102 or other flow combining system, apparatus, or method describedherein may be selected to recombine waves at 180 degrees out of phase ofa primary frequency in the range of operation of the pump (e.g., 200,450, 806, and 906) to cancel or attenuate pressure waves at thatfrequency. It should be recognized that certain harmonics of thatfrequency will also be attenuated by that tuned loop 102 or the otherflow combining systems, apparatuses, and methods described herein.

A second tuned loop 102 may be selected to recombine waves at 180degrees out of phase of a different primary frequency in the range ofoperation of the pump (e.g., 200, 450, 806, and 906) to attenuate thatfrequency and certain harmonics of that frequency.

Because a selected number of tuned loops 102 tuned to primaryfrequencies in the pump (e.g., 200, 450, 806, and 906) operating rangewill cancel frequencies for which they are tuned and certain harmonicsof those frequencies and will also attenuate frequencies near the tunedfrequencies, a small number of tuned loops 102, in many cases from twoto four tuned loops 102, may be sufficient to attenuate a range ofprimary frequencies that may be created by a pump that operates atvarying speeds to a desired level.

Frequently in fluid pumping applications, the speed range of a pump(e.g., 200, 450, 806, and 906) may be significant enough to justify theuse of two or three tuned loops 102 tuned to primary frequencies in thepump (e.g., 200, 450, 806, and 906) operating range, but not so large asto merit more than two or three tuned loops 102. A defined range ofprimary frequencies within which attenuation is desired may, therefore,be determined and a desired level of pressure wave attenuation for thatrange may be designed using a finite number of tuned loops 102.

Additional tuned loops 102 may be employed to cancel problematic orundesirable non-primary frequencies. Accordingly, networks of two,three, or four tuned loops 102 or networks that combine one or moretuned loops 102 with other flow combining systems, apparatuses, andmethods described herein are believed to be effective to minimize a widerange of undesirable frequencies in a fluid pumping application.Furthermore, other pressure wave attenuation devices, such as bottles,and methods, such as those previously used or those developed in thefuture, may be used in combination with one or more tuned loops 102 toattenuate pressure waves.

Referring again to the embodiment illustrated in FIG. 2, the cycles ofthe three cylinders 250, 252, and 254 on the first side 246 of thereciprocating compressor 200 may be offset by 60 degrees (noting thisfigure depicts a double acting compressor configuration) one fromanother. The three cylinders 256, 258, and 260 on the second side 248 ofthe reciprocating compressor 200 may also be offset by 60 degrees(noting this figure depicts a double acting compressor configuration)one from another. In addition, the cylinders on the second side 248 maybe offset from the cylinders on the first side 246 by 30 degrees suchthat pressure peaks or pulsations propagating from the second side 248cylinders 256, 258, and 260 occur at or near a midpoint in time betweenpressure peaks or pulsations propagating from the first side 246cylinders 250, 252, and 254. In that way, there can be twelve pressurepeaks or pulsations leaving the reciprocating compressor 200 at equallyspaced time intervals per rotation of the shaft 204. For example, thefirst cylinder 250 may reach peak discharge pressure on a first of itstwo strokes per cycle at 0 degrees of shaft 204 rotation, the fourthcylinder 256 may reach peak discharge pressure on a first of its twostrokes per cycle at 30 degrees of shaft 204 rotation, the secondcylinder 252 may reach peak discharge pressure on a first of its twostrokes per cycle at 60 degrees of shaft 204 rotation, the fifthcylinder 258 may reach peak discharge pressure on a first of its twostrokes per cycle at 90 degrees of shaft 204 rotation, the thirdcylinder 254 may reach peak discharge pressure on a first of its twostrokes per cycle at 120 degrees of shaft 204 rotation, and the sixthcylinder 260 may reach peak discharge pressure on a first of its twostrokes per cycle at 150 degrees of shaft 204 rotation. The firstcylinder 250 may reach peak discharge pressure on a second of its twostrokes per cycle at 180 degrees of shaft 204 rotation, the fourthcylinder 256 may reach peak discharge pressure on a second of its twostrokes per cycle at 210 degrees of shaft 204 rotation, the secondcylinder 252 may reach peak discharge pressure on a second of its twostrokes per cycle at 240 degrees of shaft 204 rotation, the fifthcylinder 258 may reach peak discharge pressure on a second of its twostrokes per cycle at 270 degrees of shaft 204 rotation, the thirdcylinder 254 may reach peak discharge pressure on a second of its twostrokes per cycle at 300 degrees of shaft 204 rotation, and the sixthcylinder 260 may reach peak discharge pressure on a second of its twostrokes per cycle at 330 degrees of shaft 204 rotation.

FIG. 3 illustrates a schematic diagram depicting another embodiment of asix cylinder reciprocating compressor 300 type pump having an offsetcylinder operation. The compressor 300 includes a motor 302 that turns acrankshaft 304. The compressor 300 may be of any desired type, includingan electrically powered or natural gas powered compressor 300.

The crankshaft 304 illustrated in FIG. 3 is coupled to a firstconnecting rod 310, a second connecting rod 312, a third connecting rod314, a fourth connecting rod 316, a fifth connecting rod 318, and asixth connecting rod 320. In various embodiments, the crankshaft 304 maybe coupled to any number of connecting rods or other piston operatingapparatuses.

The first connecting rod 310 is coupled to a first piston 330 in a firstcylinder 350. The second connecting rod 312 is coupled to a secondpiston 332 in a second cylinder 352. The third connecting rod 314 iscoupled to a third piston 334 in a third cylinder 354. The fourthconnecting rod 316 is coupled to a fourth piston 336 in a fourthcylinder 356. The fifth connecting rod 318 is coupled to a fifth piston338 in a fifth cylinder 358. The sixth connecting rod 320 is coupled toa sixth piston 340 in a sixth cylinder 360.

For simplicity, FIG. 3 shows a single simplified disc-like crank throw322, 324, and 326 for each pair of opposed cylinders 350 and 356, 352and 358, 354 and 360. Alternatively, the crank shaft 304 may have anindividual crank throw for each cylinder 350, 356, 352, 358, 354, and360 or any other crankshaft 304 configuration desired.

The reciprocating compressor 300 embodiment illustrated in FIG. 3 mayprovide better balanced inertia than the reciprocating compressor 200illustrated in FIG. 3 and other arrangements may be used that furtherimprove inertial balance. Any arrangement of cylinders may be used tomeet any number of constraints or consideration. Moreover, thereciprocating compressors 200 and 300 illustrate only certain componentsof a reciprocating compressor and additional components may be used asdesired. For example, counterweights may be used to balance therotational momentum of a reciprocating compressor (e.g., 200 or 300).

The cycles of the three cylinders 350, 352, and 354 on the first side346 of the reciprocating compressor 300 may be offset by 120 degrees(noting this figure depicts a double acting compressor configuration)one from another. The three cylinders 356, 358, and 360 on the secondside 348 of the pump 300 may also be offset by 120 degrees (noting thisfigure depicts a double acting compressor configuration) one fromanother. In addition, the cylinders on the second side 348 may be offsetfrom the cylinders on the first side 346 by 30 degrees such thatpressure peaks or pulsations propagating from the second side 348cylinders 356, 358, and 360 occur at or near a midpoint in time betweenpressure peaks or pulsations propagating from the first side 346cylinders 350, 352, and 354. In that way, there can be twelve pressurepeaks or pulsations leaving the reciprocating compressor 300 at equallyspaced time intervals per rotation of the shaft 304. For example, thefourth cylinder 356 may reach a peak discharge pressure on its strokeaway from the crankshaft 304 at 0 degrees of shaft 304 rotation, thefirst cylinder 358 may reach a peak discharge pressure on its strokeaway from the crankshaft 304 at 30 degrees of shaft 304 rotation, thefifth cylinder 358 may reach peak discharge pressure on its stroketoward the crankshaft 304 at 60 degrees of shaft 304 rotation, thesecond cylinder 352 may reach peak discharge pressure on its stroketoward the crankshaft 304 at 90 degrees of shaft 304 rotation, the sixthcylinder 360 may reach peak discharge pressure on its stroke away fromthe crankshaft 304 at 120 degrees of shaft 304 rotation, and the thirdcylinder 354 may reach peak discharge pressure on its stroke away fromthe crankshaft 304 at 150 degrees of shaft 304 rotation. The fourthcylinder 350 may reach peak discharge pressure on its stroke toward thecrankshaft at 180 degrees of shaft 304 rotation, the first cylinder 350may reach peak discharge pressure on its stroke toward the crankshaft304 at 210 degrees of shaft 304 rotation, the fifth cylinder 358 mayreach peak discharge pressure on its stroke away from the crankshaft 304at 240 degrees of shaft 304 rotation, the second cylinder 252 may reachpeak discharge pressure on its stroke away from at 270 degrees of shaft304 rotation, the sixth cylinder 360 may reach peak discharge pressureon its stroke toward at 300 degrees of shaft 304 rotation, and the thirdcylinder 354 may reach peak discharge pressure on its stroke toward thecrankshaft 304 at 330 degrees of shaft 304 rotation.

FIG. 4 illustrates an embodiment of an outlet or discharge fluid pipingsystem 440. The piping system includes a reciprocating pump 450, a flowcombination system 494, and a tuned loop 480. The reciprocating pump 450includes four cylinders 452, 454, 456, and 458, having outlets 441, 442,443, and 444 respectively. A first header 460 carries fluid flowing fromthe first outlet 441 to a first side junction 474 and a second header462 carries fluid flowing from the second outlet 442 to the first sidejunction 474. A third header 464 carries fluid flowing from the thirdoutlet 443 to a second side junction 476 and a fourth header 466 carriesfluid flowing from the fourth outlet 444 to the second side junction476. The first header 460 and second header 462 are attached to a firstbranch line 470 at a first side junction 474 and the third header 464and fourth header 466 are attached to a second branch line 472 at asecond side junction 476. The first inlet branch line 470 and secondinlet branch line 472 are attached to an inlet of the tuned loop 480 ata branch junction 478.

A connecting conduit 490 leads from the branch junction 478 to an inletof a tuned loop inlet junction 486. The tuned loop inlet junction 486also has two outlets, the first outlet being attached to a first end afirst attenuating conduit 482 of the tuned loop 480 and the secondoutlet being attached to a first end of a second attenuating conduit 484of the tuned loop 480. A second end of the first attenuating conduit 482is attached to a first inlet of a tuned loop outlet junction 488 and asecond end of the second attenuating conduit 482 is attached to a secondinlet of the tuned loop outlet junction 488. An outlet of the tuned loopoutlet junction is attached to a discharge conduit 492.

In an embodiment of the reciprocating pump system 440 the reciprocatingpump 450 includes four double-acting cylinders 452, 454, 456, and 458.Each double-acting cylinder 452, 454, 456, and 458 causes fluid to flowtwice during each rotation of a shaft 496 turned by a motor 498 anddriving the reciprocating pump 450, thus creating pressure variations inthe form of waves in the fluid propagating through the flow combinationsystem 494 and the tuned loop 480 at twice the frequency of the shaft496 rotation. In one embodiment, pairs of those cylinders 452 and 456,454 and 458 create flow simultaneously (one on the upstroke and theother on the down-stroke) and the pairs of cylinders 452 and 454, 456and 458 operate at 90° out of phase. In such an arrangement, the outlets441 and 442 of two cylinders 452 and 454 operating at 90° of shaft 496rotation out of phase (and creating fluid pressure waves which, at twicethe shaft 496 rotation frequency, are 180° out of phase) are coupledusing short, equal length header pipes 460 and 462 to quickly interleavethe primary wavelength pressure waves existing in the fluid flow createdby those cylinders 452 and 454. The outlets 443 and 444 of the other twocylinders 456 and 458 operating at 90° out of phase are similarlycoupled using short, equal length header pipes 464 and 466 to quicklyinterleave the primary wavelength pressure wave existing in the fluidflow created by those cylinders 456 and 458.

In the embodiment illustrated in FIG. 4, cylinders, 452 and 454, containdouble acting pistons which produce pressure waves that have two peaks180° apart for every complete rotation of the crankshaft. The troughs onthe pump crankshaft for cylinders 452 and 454 are offset by 90 crankangle degrees. The first header 460, carrying the fluid flow andpressure wave from the first cylinder 452, and the second header 462,carrying the fluid flow pressure wave from the second cylinder 454, areof equal length and join at a first side junction 474. In that way, theflows and pressure waves of the first cylinder 452 and second cylinder454 are combined at 90° out of phase, thus interleaving, andsignificantly attenuating, pressure waves propagating from the first andsecond cylinders 452 and 454 and through the first and second headers460 and 462 as the flow and pressure waves proceed down stream ofjunction 474 in conduit 470.

Pressure waves emanating from the third cylinder 456 and the fourthcylinder 458 on a second side 448 of the pump 450 are also 180° out ofphase. The third header 464, carrying fluid flow from the third cylinder456, and the fourth header 466, carrying fluid flow from the fourthcylinder 458, are of equal length and the flows through those headers464 and 466 join at a second side junction 476. In that way, the flowsof the third cylinder 456 and fourth cylinder 458 are combined at 180°out of phase, thus interleaving, and thereby cancelling or at leastsignificantly attenuating, pressure waves flowing from the third andfourth cylinders 456 and 458 and through the third and fourth headers464 and 466.

In the embodiment illustrated in FIG. 4, pistons in the first cylinder452 and the third cylinder 456 operate in phase and pistons in thesecond cylinder 454 and the fourth cylinder 458 operate in phase suchthat pressures at the outlets 441 and 443 of the first and thirdcylinders 452 and 456 follow similar cycles and pressures at thedischarges 442 and 444 of the second and fourth cylinders 454 and 458follow similar cycles.

In another embodiment, the cycles of the first cylinder 452 and thethird cylinder 456 are offset 45 degrees of shaft 496 rotation from oneanother and the cycles of the second cylinder 454 and the fourthcylinder 458 are offset 45 degrees of shaft 496 rotation from oneanother. In that way, pressure peaks from the first cylinder 452 to thesecond cylinder 454 are offset by 90 degrees of shaft rotation, whichcorresponds to a 180 degree wave phase offset, such that peak highpressure from the first cylinder 452 coincides with low pressure fromthe second cylinder 454. Pressure peaks from the second cylinder 454 tothe third cylinder 456 are also offset by 90 degrees of shaft rotationand 180 degrees of wave phase such that peak high pressure from thesecond cylinder 454 coincides with low pressure from the third cylinder456. Pressure peaks from the third cylinder 456 to the fourth cylinder458 are also offset by 90 degrees of shaft rotation and 180 degrees ofwave phase such that peak high pressure from the third cylinder 456coincides with low pressure from the fourth cylinder 458. Pressure peaksfrom the fourth cylinder 458 to the first cylinder 452 are also offsetby 90 degrees of shaft rotation and 180 degrees of wave phase such thatpeak high pressure from the fourth cylinder 458 coincides with lowpressure from the first cylinder 452.

In an embodiment headers leading from the first cylinder 452, secondcylinder 454, third cylinder 456, and fourth cylinder 458 may becombined directly, for example at the first side junction 474 by equallength headers 460, 462, 464, and 466 in certain embodiments, or inanother way designed to attenuate pressure waves in the fluid flowingthrough those headers 460, 462, 464, and 466 and the second sidejunction 476 may not be used.

A first branch line 470 extends from the first side junction 474 wherethe first header 460 from the first cylinder 452 is coupled to thesecond header 462 from the second cylinder 454. A second branch line 472extends from the second side junction 476 where the third header 464from the third cylinder 456 is coupled to the fourth header 466 from thefourth cylinder 458. Those first and second branch lines 472 and 474 arefurther coupled at a branch line junction 478.

The lengths of the first branch line 470 and second branch line 472 arearranged such that the fluid flow in the first branch line 470 iscoupled to the fluid flow from the second branch line 472 at the branchline junction 478 at 45° out of phase for a desired frequency.

Thus, the lengths of branch line 470 and branch line 472 in thatembodiment are different. Moreover, the difference in the lengths ofbranch lines 470 and 472 is arranged so that a pulsation frequencyexperienced in the fluid flowing through the first branch line 470and/or the second branch line 472 is interleaved and attenuated at thebranch line junction 474.

Another consideration in determining the length of headers 460, 462,464, and 466 and branch lines 470 and 472 is the effect of pressurewaves traveling upstream to one or more cylinders 452, 454, 456, and458. Wave peaks may, for example, be created when a piston is movingtoward or when a piston reaches either end of a cylinder (for examplecylinder 452) in a double-acting cylinder. Those wave peaks may affectthe operation of one or more other cylinders (for example, cylinders454, 456, or 458) as they propagate through the piping system 440 andreach those cylinders (for example, cylinders 454, 456, or 458). Itshould be recognized that each cylinder 452, 454, 456, and 458 willcreate pressure waves that may include pulses or wave peaks when theyoperate and those pressure waves will affect the other operatingcylinders 452, 454, 456, and 458. Those pressure waves, furthermore,move along the piping system 440 at a regular frequency when thecylinders 452, 454, 456, and 458 operate at a constant speed. Thus, thetime between wave peaks can be determined for a cylinder 452, 454, 456,and 458 operating at a constant speed, the time it takes for pressurewaves to move along a length of pipe may be determined, and the timesand regularity at which pressure peaks will arrive at a cylinder 452,454, 456, and 458 can be determined.

Accordingly, header 460, 462, 464, and 466 and/or branch line 470 and472 length can affect the efficiency at which the cylinders 452, 454,456, and 458 operate and header 460, 462, 464, and 466 and/or branchline 470 and 472 length can be selected to optimize efficiency or otheroperating conditions existing at cylinders 452, 454, 456, and 458.

Pressure waves created by operation of the cylinders 452, 454, 456, and458 propagate upstream and downstream in the headers 460, 462, 464, and466 and branch lines 470 and 472 illustrated in FIG. 4. Accordingly,pressure waves from the first cylinder 452 partially impinge or comeinto contact with other cylinders 454, 456, and 458 in the piping system440 and can affect the operation of those cylinders 454, 456, and 458.Likewise, pulse waves emanating from the other cylinders 454, 456, and458 will partially impinge or come into contact with other cylinders452, 454, 456, and 458 connected to the piping system 440 and can affectthe operation of those cylinders 452, 454, 456, and 458.

For example, pressure waves created by the motion of a piston (e.g., 230in FIG. 2) in the first cylinder 452 may propagate along the firstheader 460 and at least partially upstream along the second header 462to the second cylinder 454. Those pressure waves may also propagate atleast partially through the first side junction 474, along first branchline 470, through the branch line junction 478, upstream along thesecond branch line 472, through the second side junction 476 and alongboth the third header 464 and the fourth header 466 to contact orimpinge upon the third cylinder 456 and the fourth cylinder 458.

Thus, in an embodiment, first and second headers 460 and 462 can havelengths selected to optimize the effect on the second cylinder 454 frompulses or pressure waves propagating from the first cylinder 452 and tooptimize the effect on the first cylinder 452 from pulses or pressurewaves propagating from the second cylinder 454. Similarly, the third andfourth headers 464 and 466 can have lengths selected to optimize theeffect on the fourth cylinder 458 from pulses or pressure wavespropagating from the third cylinder 456 and to optimize the effect onthe third cylinder 456 from pulses or pressure waves propagating fromthe fourth cylinder 458.

The lengths of the first and second headers 460 and 462 can bemaintained equal in an embodiment, while the total length of the firstand second headers 460 and 462 combined is determined to optimize theeffect of the pressure waves propagating from the first cylinder 452 onthe second cylinder 454 and to optimize the effect of the pressure wavespropagating from the second cylinder 454 on the first cylinder 452.

Similarly, the lengths of the third and fourth headers 464 and 466 canbe maintained equal in that embodiment, while the total length of thethird and fourth headers 464 and 466 combined is determined to optimizeor reduce the effect of the pressure waves propagating from the thirdcylinder 456 on the fourth cylinder 458 and to optimize the effect ofthe pressure waves propagating from the fourth cylinder 458 on the thirdcylinder 456.

Thus, the length of each of the first and second branch lines 470 and472 may be determined to attenuate pressure waves or pulsationspropagating through those lines 470 and 472 by combining the flowpassing through those lines 470 and 472 at branch line junction 478 whenthe flows passing through those lines will cancel or attenuate undesiredpressure waves or pulsations. Alternately or in addition, the lengths ofbranch lines 470 and 472 may be arranged to optimize the effect of pulsewaves propagating from the first side junction 474 at least partially tothe third and fourth cylinders 456 and 458 and to optimize the effect ofpulse waves propagating from the second side junction 476 at leastpartially to the first and second cylinders 452 and 454.

In a system where first, second, third, and fourth cylinders 452, 454,456, and 458 are driven by a common shaft 496 and motor 498, as isdepicted in FIG. 4, and where opposing cylinders, such as the firstcylinder 452 and third cylinder 456 (and the second cylinder 454 andfourth cylinder 458) are operating in phase (the pistons in the in phasecylinders 452 and 456, 454 and 458 reach one of the two ends of theirstrokes simultaneously or nearly simultaneously), the total branch linelength (length of the first branch line 470 plus length of the secondbranch line 472 and, possibly, plus a length associated with the branchline junction 478) may be selected to optimize the effect of pulse waveson both the cylinders on the first side 446 and second side 448 of thepump 450.

For example, the combined length of the first header 460, the firstbranch line 470, the second branch line 472 and the third header 464(plus junctions 474, 478, and 476 if applicable) may be selected suchthat pulsations or undesirable portions of a pressure wave emanating orpropagating from the first cylinder 452 arrive at the third cylinder 456at a time in the third cylinder 456 cycle when those pulsations orundesirable portions of a pressure wave have a less detrimental effecton the operation of the third cylinder 456. The combined length of thefirst header 460, the first branch line 470, the second branch line 472and the fourth header 466 may also be selected to minimize or reduce anydetrimental effect of the operation of the first cylinder 452 on thefourth cylinder 458.

Because the cycles of the third and fourth cylinders 456 and 458 may beoffset one from the other and the lengths of the third and fourthheaders 464 and 466 may be equal or otherwise arranged such that it isnot practical or possible to have pulsations or undesirable portions ofa pressure wave arrive at both the third and fourth cylinders 456 and458 at an optimal time, a compromise in combined line (e.g., 460, 470,472, 464, or 460, 470, 472, 466, or 462, 470, 472, 464, or 462, 470,472, 466) length may be made such that combined operation of the thirdand fourth cylinders 456 and 458 is improved or optimized, rather thanoptimization of one or the other cylinder 456 and 458. Thus, forexample, where the pressure waves of the third cylinder 456 are offsetfrom the pressure waves of the fourth cylinder 458 by 90 degrees ofshaft rotation and the third header 464 and the fourth header 466 are ofequal length, the combined lengths of the lines 460, 470, 472, 464, and460, 470, 472, 466 leading from the first cylinder 452 to the third andfourth cylinders 456 and 458 may be arranged such that pulsations orundesirable portions of a pressure wave emanating from the firstcylinder 452 arrive at the third and fourth cylinders 456 and 458 atmid-cycle for both the third and fourth cylinders 456 and 458 or anotherdesirable time in the cycles of the third and fourth cylinders 456 and458.

Because the cycles of the first and second cylinders 452 and 454 may beoffset one from the other and the lengths of the first and secondheaders 460 and 462 may be equal or otherwise arranged such that it isnot practical or possible to have pulsations or undesirable portions ofa pressure wave emanating or propagating from the first and secondcylinders 452 and 454 arrive at the third or fourth cylinders 456 and458 at an optimal time, a compromise in combined line 460, 470, 472,464, or 460, 470, 472, 466, or 462, 470, 472, 464, or 462, 470, 472, 466length may be made such that combined operation of the cylinders 452,454, 456 and 458 is improved or optimized, rather than optimization ofany subset of those cylinders 452, 454, 456 and 458. Thus, for example,where the pressure waves of the first cylinder 452 are offset from thepressure waves of the second cylinder 454 by 90 degrees of shaftrotation the pressure waves of the third cylinder 456 are offset fromthe pressure waves of the fourth cylinder 458 by 90 degrees, the firstheader 460 and the second header 462 are of equal length and the thirdheader 464 and the fourth header 466 are of equal length, the combinedlengths of the lines leading from one cylinder (e.g., 452, 454, 456, or458) to one or more other cylinders (e.g., 452, 454, 456, or 458) may bearranged such that pulsations or undesirable portions of a pressurewaves emanating from each cylinder (e.g., 452, 454, 456, or 458) arriveat each other cylinder (e.g., 452, 454, 456, or 458) at a desirable timein the cycles of those other cylinders (e.g., 452, 454, 456, or 458).

In one embodiment of the outlet (discharge) piping system 440, thelength of the first and second headers 460 and 462 is selected such thata low pressure point of a wave created by a piston (e.g., 230 in FIG. 2)in the first cylinder 452 moves along the first header 460, the firstside junction 474, and the second header 462 and arrives at the secondcylinder 454 at a time when a piston in the second cylinder 454 is at ornear an end of its stroke (i.e. either end for a double-acting piston)and thus near either end of the cylinder and thus not near the center ofits stroke. Such an arrangement may increase gas flow capacity. Inanother embodiment, the lengths of the first and second headers 460 and462 may be selected such that a low pressure point of a wave created bya piston (e.g., 230 in FIG. 2) in the first cylinder 452 moves along thefirst header 460, the first side junction 474, and the second header 462and arrives at the second cylinder 454 at a time when a piston in thesecond cylinder 454 is at or near the middle of its stroke (in adouble-acting piston). Such an arrangement may improve compressorefficiency.

Note that in an embodiment in which the piston is a single-acting pistonin an outlet or discharge piping system 440, the above regarding adouble-acting cylinder may apply, except that for increased gas flowcapacity, the low pressure point of the wave may arrive at the secondcylinder 454 when the piston in the second cylinder 454 is at or nearthe end of its stroke, and thus the end of the second cylinder 454 wherethe piston is finishing or has just finished expelling gas from thesecond cylinder 454. For increased efficiency, the above regarding adouble-acting cylinder may apply, except that the low pressure point ofthe wave may arrive at the second cylinder 454 when the piston in thesecond cylinder 454 is at or near the middle of its stroke moving in adirection in which it is pushing gas out of the second cylinder 454.

As used herein in relation to a piston stroke on the outlet or dischargeside of a piping system, “at or near an end” or a similar term regardinga piston stroke refers to (for a double-acting piston) a position of thepiston closer to either end of the cylinder than the middle of thecylinder, and refers to (for a single-acting piston) a position of thepiston closer to the end of the cylinder where the piston is finishingor has just finished expelling gas. That term or a similar term thusencompasses both a single-acting and double-acting cylinder and pistonunless otherwise specified.

As used herein in relation to a piston stroke on the outlet or dischargeside of a piping system, “at or near the middle” or a similar termregarding a piston stroke refers to (for a double-acting piston) aposition of the piston closer to the middle of the cylinder than eitherend of the cylinder, and refers to (for a single-acting piston) aposition of the piston closer to the middle of the cylinder when thepiston is moving in a direction in which it is pushing gas out of thecylinder. That term or a similar term thus encompasses both asingle-acting and double-acting cylinder and piston unless otherwisespecified.

It may be recognized that pressure waves and pulses may propagate alongall the pipes 460, 462, 464, 466, 470, 472, 482, 484, 490, and 492 inthe system 440 and to all apparatuses connected to the piping system 440including any cylinders of additional pumps (not shown) that areconnected to the piping system 440. The lengths of the headers 460, 462,464, and 466 and various pipes 470, 472, 482, 484, 490, and 492 may,therefore, be selected such that pressure waves or pulses passingthrough the piping system 440 arrive at cylinders 452, 454, 456, and 458and any other cylinders present in the piping system 440 at times thatare beneficial or at least minimally detrimental to operation of thecylinders 452, 454, 456, and 458 and any other cylinders present in thepiping system 440. Such an arrangement may improve efficiency, fluidflow, power consumption, or other operational aspects of cylinders (suchas cylinders 454, 456, or 458) based on pulse waves propagating fromanother cylinder (such as cylinder 452). The lengths of the headers 460,462, 464, and 466 and various pipes 470, 472, 482, 484, 490, and 492may, therefore, be selected such that pressure waves and pulses passingthrough the piping system 440 arrive at any selected portion of thepiping system 440 or anything connected to the piping system 440 at adesired time.

It should be recognized that headers 460, 462, 464, 466 and branch lines470 and 472 may be devised in various lengths and sizes to combine fluidflow from multiple cylinders (including cylinders 452, 454, 456, and458) or multiple pumping devices (including pump 450) to cancel andattenuate undesirable frequencies created by those cylinders (includingcylinders 452, 454, 456, and 458) and pumps (including pump 450) havingvarious arrangements. Thus, headers (including headers 460, 462, 464,466) may have unequal lengths to combine flows that do not havefrequencies of 180° out of phase. Branch lines 470 and 472 may also havevaried lengths and sizes to cancel and attenuate pressure waves orfrequencies other than those that are 180° out of phase.

For example, in the embodiment illustrated in FIG. 4, the first andsecond headers 460 and 462 may be the same length to combine thepressure waves propagating from the first and second cylinders 452 and454 at 180 degrees out of phase. Similarly, the third and fourth headers464 and 466 may be the same length to combine the pressure wavespropagating from the third and fourth cylinders 456 and 458 at 180degrees out of phase. While pulsations or pressure waves in a primarywavelength created by the first and second cylinders 452 and 454 and oddharmonics of that primary wavelength may be cancelled or attenuated bysuch a combination of the flows propagating from the first and secondcylinders 452 and 454, pulsations or pressure waves in other undesirablewavelengths may still exist in the combined flow leaving the first sidejunction 474. Similarly, pulsations or pressure waves in a primarywavelength created by the third and fourth cylinders 456 and 458 and oddharmonics of that primary wavelength may be cancelled or attenuated by asimilar combination of the flows propagating from the third and fourthcylinders 456 and 458 at 180 degrees out of phase. Nonetheless, pressurewaves or pulsations in other undesirable wavelengths may still exist inthe combined flow leaving second side junction 476. The pulsations orpressure waves may, furthermore, exist in various undesirablewavelengths because, for example, the pump 450 may be a reciprocatingcompressor that operates at various speeds or with certain cylinders452, 454, 456, and 458 unloaded and configurations where flow orpressure waves is not smooth or similar but opposite on opposites sidesof a pressure peak because, for example, of the operation of pistons(e.g., 230, 232, 234, 236, 238, 240, 330, 332, 334, 336, 338, and 340)working in conjunction with inlets and outlets at various pressures.Accordingly, the difference in the lengths of the first and secondbranch lines 470 and 472 may be selected to cancel or attenuate aprimary wavelength remaining after the combination of the flows at thefirst side junction 474 and the second side junction 476. In anembodiment, such as that depicted in FIG. 4, where the pump 450 mayoperate at various speeds or with certain cylinders 452, 454, 456, and458 unloaded, the wavelength selected to be cancelled or attenuated atbranch line junction 478 may be selected to attenuate pressure waves orpulsations created at a mid-portion of the range of operation of thepump 450.

Junctions 474, 476, 478, 486, and 488, terminations, restrictions,certain bends, changes in pipe cross-sectional area, atmosphericdischarge points and other piping system 440 components or features mayreflect pressure waves and pulses upstream, for example back to the pump450. Thus, the downstream waves, or waves propagating in the directionof fluid flow out of the pump 450, may, at those components andfeatures, be partially reflected or otherwise travel back, or upstream,toward the discharge side of the pump 450. The downstream waves andreflected or otherwise formed upstream waves superimpose and may bemeasured together by a pressure transducer, while neither may beseparately measurable by a pressure transducer. However, those waves maybe otherwise tracked, such as by gas flow simulation software in oneembodiment. That software may be, for example, the one dimensional gasflow simulation software developed by OPTIMUM Power Technology. Adesigner can use the gas flow simulation software to observe the effectof positioning the junctions and other piping components that mayreflect pressure waves and thus determine the pipe lengths extending tothose components that cause the upstream waves so as to affect theperformance of the pump 450 and piping system 440. Depending upon thepositioning of the junctions and reflective components and the pipelengths used to attach those reflective components to the system, systemperformance criteria, such as flow rate or efficiency, may be improved.

In one embodiment, for example, the fluid pumping system 440 may be mademore efficient by locating junctions 474, 476, 478, 486, and 488 atappropriate positions in relation to the pump 450 or other components ofthe piping system 440. For example, the side junctions 474, 476 may belocated at an appropriate distance from the pump 450 to reflect pressurewaves back to the pump 450 outlet of one or more cylinders 452, 454,456, and 458 of the pump 450 such that those waves are at a low or lowerpressure point at the cylinder outlets 441, 442, 443, and 444 when thepistons of the cylinders 452, 454, 456, and 458 are at a higher velocityor at or near the middle of the piston stroke. Such a phase arrangementmay decrease the energy needed to cause the piston to move the sameamount of fluid flow out of the pump, and thus increase pump and systemefficiency.

Alternatively, in another embodiment, the fluid pumping system 440 mayincrease flow capacity by locating junctions 474, 476, 478, 486, and 488at appropriate positions in relation to the pump 450 or other componentsof the piping system 440. For example, the side junctions 474, 476 maybe located at an appropriate distance from the pump 450 to reflectpressure waves back to the pump 450 outlet of one or more cylinders 452,454, 456, and 458 of the pump 450 such that those waves are at a low orlower pressure point at the cylinder outlets 441, 442, 443, and 444 whenthe pistons of the cylinders 452, 454, 456, and 458 are at a lowervelocity, for example the pistons in those cylinders 452, 454, 456, and458 may be at or near the ends of their strokes. Such a phasearrangement may increase flow rate.

In embodiments, the location of any combination of the junctions 474,476, 478, 486, and 488 can be adjusted to increase flow capacity orimprove pump 450 efficiency. Note that, as described above, variouscomponents and features of the piping system 440 may each cause wavereflections. Those components and features may be thus be adjusted suchthat the total, superimposed reflected or otherwise upstream-moving waveis at a low or lower pressure point at the cylinder outlets 441, 442,443, and 444 when the cycles of the cylinders 452, 454, 456, and 458 areat a higher velocity at or near the middle of the piston strokes (forefficiency) or a lower velocity at or near the ends of the pistonstrokes (for increased flow capacity) or at any desired point in thecycles of the cylinders 452, 454, 456, and 458 or stroke of the pistonsin the cylinders 452, 454, 456, and 458.

The time it takes for a reflected wave to reach a destination variesdependent upon the lengths of conduits extending between a reflectivecomponent and the destination and the acoustic velocity of the fluid.Thus, for example, the time required for a wave reflected from the firstside junction 474 to the first cylinder outlet 452 outlet 441 willdepend on the length of the first header 460 and the acoustic velocityof the fluid flowing through the first header 460 and carrying the wave.

In embodiments, gas flow simulation software, for example, may be usedto specify the location of one or more other junctions (e.g., 478, 488)to reduce or otherwise affect pressure at the outlet of one or morecylinders 452, 454, 456, and 458 of the pump 450, recognizing that wavespartially reflected back upstream (e.g. at junction 488) may themselvesbe partially reflected back downstream as they encounter junctions (e.g.478, 474, 476) on their way upstream toward the pump 450. Suchadditional reflections may be simulated by, for example, the onedimensional gas flow simulation software developed by OPTIMUM PowerTechnology or other software.

In one embodiment, the length of pipe (e.g., headers 460, 462, 464, and466) extending from a cylinder outlet (e.g., 441, 442, 443, and 444) toa first junction (e.g., 474 and 476) may be determined to produce thedesired operation of the pump 450 (e.g., high flow, low powerconsumption, a desired flow at a desired power consumption, or otherdesired combination operating characteristics). Next, the length of apipe (e.g., branch lines 470 and 472) extending from the first junction(e.g., 474 and 476) to a second junction (e.g., 478) may be determinedto produce the desired operation of the pump 450.

Additionally, the aforementioned positioning of junctions andspecification of pipe lengths and other specifications that may affectpressure at a pump based on reflected waves may be applied to systemsother than the piping system 440 of FIG. 4. Thus, for example, in anembodiment the piping system 540 of FIG. 5 may be designed using the onedimensional gas flow simulation software developed by OPTIMUM PowerTechnology or other software to specify locations of junctions 574, 576,578, 586, and/or 588 to reduce or otherwise affect pressure at the pump550 based, at least in part, on reflected waves. Similarly, in theembodiment of the six-cylinder reciprocating compressor type pump 694system 600, that software may be used to specify locations of junctions660, 662, and/or 678 to reduce or otherwise affect pressure at the pump550 based, at least in part, on reflected waves.

Further attenuation may be accomplished by adding one or more tunedloops, such as tuned loop 480 illustrated in FIG. 4, to the pipingsystem 440 to attenuate one or more additional frequencies of pressurewaves or pulsations in the fluid flowing through the piping system 440.The tuned loops 480 may be located anywhere desired in the piping system440, such that the tuned loop 480 may, for example, be located in orbetween the headers 460, 462, 464, and 466 and in or between the branchlines 470 and 472.

The tuned loop 480 illustrated in FIG. 4 includes or is attached to theconnecting conduit 490 leading from the branch line junction 478 andcoupled at its discharge to the tuned loop inlet junction 486. It isnoted that the branch line junction 478 may be attached directly to theinlet junction 486 and the inlet conduit 490 may not be used in anembodiment. The inlet junction 486 is coupled to a first or inlet end ofa first attenuating conduit 482 and a first or inlet end of a secondattenuating conduit 484. The first and second attenuating conduits 482and 484 are coupled to an outlet junction 488 at their second ordischarge ends and the outlet junction 488 discharges into the dischargeconduit 492.

A pressure wave or pulsation attenuation system, such as the pipingsystem 440 illustrated on the outlet side of the pump 450 in FIG. 4 mayalternately or in addition be used on the inlet (e.g., 804 and 904 asshown in FIGS. 8 and 9) side of a pump such as the pump 450 in FIG. 4.Thus, all or any part of the piping system 440 illustrated on the outletside of the pump 450 in FIG. 4 may be applied to the pump 450 inlet(e.g., 804 and 904 as shown in FIGS. 8 and 9), the pump 450 outlet(e.g., 808 and 908 as shown in FIGS. 8 and 9), or both the inlet and theoutlet of the pump 450. Moreover, a piping system 440 may combine flowfrom cylinders 452, 454, 456, and 458 of more than one pump 450 so that,for example, headers may combine flows from different pumps (includingpump 450 and one or more other pumps not illustrated) or differentcylinders (including cylinders 452, 454, 456, and 458 and one or moreother cylinders not illustrated) of different pumps (e.g., pump 450 andone or more other pumps not illustrated) and branch lines (e.g., 470 and472) may combine flows from different pumps (including pump 450 and oneor more other pumps not illustrated) or different cylinders (includingcylinders 452, 454, 456, and 458 and one or more other cylinders notillustrated) of different pumps (including pump 450 and one or moreother pumps not illustrated).

It should also be recognized that traditional pulsation dampeningdevices, such as bottles, may be incorporated into the fluid pumpingsystem 440 if desired.

FIG. 5 illustrates an inlet piping system 540 that may operate on inletfluids similar to way the outlet piping system 540 illustrated in FIG. 4operates on outlet fluids and may be used on the same pump 450 withwhich the outlet piping system operates.

The inlet piping system 540 is connected to inlets 541, 542, 543, and544 of the cylinders 552, 554, 556, and 558 of the pump 550 illustratedin FIG. 5. Thus, the pump 550 cylinders 552, 554, 556, and 558 includeinlets 541, 542, 543, and 544, respectively. The cylinder inlets 541,542, 543, and 544 are attached to a first inlet header 562, a secondheader 560, a third inlet header 566, and a fourth inlet header 564,respectively. The first inlet header 562 and second inlet header 560 areattached to a first inlet branch line 570 at a first side inlet junction574 and the third inlet header 566 and fourth inlet header 564 areattached to a second inlet branch line 572 at a second side inletjunction 576. The first inlet branch line 570 and second inlet branchline 572 are attached to an inlet tuned loop 580 at a branch junction578.

A connecting conduit 590 leads to the inlet branch line junction 578from an outlet of a tuned loop inlet junction 586. The tuned loop inletjunction 586 also has two inlets, the first inlet being attached to afirst end a first attenuating conduit 582 of the tuned loop 580 and thesecond inlet being attached to a first end of a second attenuatingconduit 584 of the tuned loop 580. A second end of the first attenuatingconduit 582 is attached to a first outlet of a tuned loop inlet junction588 and a second end of the second attenuating conduit 582 is attachedto a second outlet of the tuned loop inlet junction 588. An inlet of thetuned loop inlet junction is attached to a supply conduit 592.

The tuned loop 580 may operate to cancel or attenuate pressure waves orpulsations propagating through the fluid flowing toward the pump 550.Those pressure waves or pulsations propagating through the fluid may becreated by the pump 550 or by one or more other system features (notshown) acting on the fluid flow either upstream or downstream of thetuned loop 580. The inlet branch lines 570 and 572 can similarly operateto cancel or attenuate pressure waves or pulsations propagating throughthe fluid flowing toward the pump 550 and the inlet headers 560, 562,and 564, 566 may operate to cancel or attenuate pressure waves orpulsations propagating through the fluid flowing toward the pump 550.

In an embodiment, the inlet (suction) piping system 540 may beconfigured to increase gas flow capacity. Thus, for a double-actingpiston arrangement, the resultant pressure wave propagating toward oneor more of the cylinders 552, 554, 556, and 558 is at a higher or highpressure point at one or more of the inlets 541, 542, 543, and 544 whenthe piston of its corresponding cylinder 552, 554, 556, or 558 is at ornear the end of its stroke. For a single-acting piston arrangement, theresultant pressure wave propagating toward one or more of the cylinders552, 554, 556, and 558 is at a higher or high pressure point at one ormore of the inlets 541, 542, 543, and 544 when the piston of itscorresponding cylinder 552, 554, 556, or 558 is at or near the end ofits stroke moving in the direction in which it is suctioning gas intothe cylinder.

In an embodiment, the inlet (suction) piping system 540 may beconfigured to increase efficiency. Thus, for a double-acting pistonarrangement, the resultant pressure wave propagating toward one or moreof the cylinders 552, 554, 556, and 558 is at a higher or high pressurepoint at one or more of the inlets 541, 542, 543, and 544 when thepiston of its corresponding cylinder 552, 554, 556, or 558 is at or nearthe middle of its stroke. For a single-acting piston arrangement, theresultant pressure wave propagating toward one or more of the cylinders552, 554, 556, and 558 is at a higher or high pressure point at one ormore of the inlets 541, 542, 543, and 544 when the piston of itscorresponding cylinder 552, 554, 556, or 558 is at or near the middle ofits stroke moving in the direction in which it is suctioning gas intothe cylinder.

As used herein in relation to a piston stroke on the inlet (suction)side of a piping system, “at or near an end” or a similar term regardinga piston stroke refers to (for a double-acting piston) a position of thepiston closer to either end of the cylinder than the middle of thecylinder, and refers to (for a single-acting piston) a position of thepiston closer to the end of the cylinder where the piston is finishingor has just finished suctioning gas. That term or a similar term thusencompasses both a single-acting and double-acting cylinder and pistonunless otherwise specified.

As used herein in relation to a piston stroke on the outlet side of apiping system, “at or near the middle” or a similar term regarding apiston stroke refers to (for a double-acting piston) a position of thepiston closer to the middle of the cylinder than either end of thecylinder, and refers to (for a single-acting piston) a position of thepiston closer to the middle of the cylinder when the piston is moving ina direction in which it is suctioning gas into the cylinder. That termor a similar term thus encompasses both a single-acting anddouble-acting cylinder and piston unless otherwise specified.

FIG. 6 illustrates an embodiment of a six-cylinder reciprocatingcompressor type pump 694 system 600. A first cylinder 602 has a firstoutlet 622 connected to a first header 642, a second cylinder 604 has asecond outlet 624 connected to a second header 644, a third cylinder 606has a third outlet 626 connected to a third header 64, a fourth cylinder608 has a fourth outlet 628 connected to a fourth header 648, a fifthcylinder 610 has a fifth outlet 630 connected to a fifth header 650, anda sixth cylinder 612 has a sixth outlet 632 connected to a sixth header652.

The pump 694 is operated by a motor 698 driving a shaft 696 that causespistons (e.g., 230, 232, 234, 236, 238, 240, 330, 332, 334, 336, 338,and 340 illustrated in FIGS. 2 and 3) to reciprocate in each of thecylinders 602, 604, 606, 608, 610, and 612. While the cylinders 602,604, 606, 608, 610, and 612 may be arranged in any way desired, thecylinders 602, 604, 606, 608, 610, and 612 in the embodiment illustratedin FIG. 6 are arranged with three cylinders 602, 604, and 606 on a firstside 616 of the pump 694 and three other cylinders 608, 610, and 612 ona second side 618 of the pump 694.

The first, second and third headers 642, 644, and 646, respectively, areattached to inlets of a first side junction 660 in FIG. 6, but the fluidflowing through the first, second and third headers 642, 644, and 646could otherwise be combined by placing those fluid flows in fluidcommunication through multiple junctions or otherwise as desired.Similarly, The fourth, fifth and sixth headers 648, 650, and 652 areattached to inlets of a second side junction 662 in FIG. 6, but thefluid flowing through the fourth, fifth and sixth headers 648, 650, and652 could also otherwise be combined by placing those fluid flows influid communication as desired. A first branch line 670 carries thefluid flow from the first side junction 660 to a branch line junction678 and a second branch line 672 carries the fluid flow from the secondside junction 662 to the branch line junction 678. The fluid then flowsfrom the branch line junction 678 to an outlet conduit 680 or,alternately, to a desired system (not shown).

In an embodiment where peak pressure waves, also referred to as a typeof pulsation, are offset, the lengths of the branch lines 670 and 672may be equal. When such equal length branch lines 670 and 672 used inconjunction with cylinders 602, 604, 606, 608, 610, and 612 havingoffset operation (such as the offset cylinder operation illustrated anddiscussed in connection with FIGS. 2 and 3), the branch lines 670 and672 may be effective to cancel or attenuate pressure waves at varyingpump 694 speeds.

For example, in the embodiment depicted in FIG. 6, the cycles of thethree cylinders 602, 604, and 606 on the first side 616 of the pump 694may be offset by 60 degrees of shaft rotation (in a double actingcompressor configuration) one from another. The three cylinders 608,610, and 612 on the second side 618 of the pump 694 may also be offsetby 60 degrees of shaft rotation (in a double acting compressorconfiguration) one from another. In addition, the cylinders 602, 604,and 606 on the first side 616 may be offset from the cylinders 608, 610,and 612 on the second side 618 by 30 degrees such that pressure peaks orpulsations from the second side 618 cylinders 608, 610, and 612 occur ator near a midpoint in time between pressure peaks or pulsations from thefirst side 616 cylinders 602, 604, and 606. In that way, there can betwelve pressure peaks or pulsations leaving the pump 694 at equallyspaced time intervals per rotation of the shaft 696. For example, thefirst cylinder 602 may reach peak discharge pressure on a first of itstwo strokes per cycle at 0 degrees of shaft 696 rotation, the fourthcylinder 608 may reach peak discharge pressure on a first of its twostrokes per cycle at 30 degrees of shaft 696 rotation, the secondcylinder 604 may reach peak discharge pressure on a first of its twostrokes per cycle at 60 degrees of shaft 696 rotation, the fifthcylinder 610 may reach peak discharge pressure on a first of its twostrokes per cycle at 90 degrees of shaft 696 rotation, the thirdcylinder 606 may reach peak discharge pressure on a first of its twostrokes per cycle at 120 degrees of shaft 696 rotation, and the sixthcylinder 612 may reach peak discharge pressure on a first of its twostrokes per cycle at 150 degrees of shaft 696 rotation. The firstcylinder 602 may reach peak discharge pressure on a second of its twostrokes per cycle at 180 degrees of shaft 696 rotation, the fourthcylinder 608 may reach peak discharge pressure on a second of its twostrokes per cycle at 210 degrees of shaft 696 rotation, the secondcylinder 604 may reach peak discharge pressure on a second of its twostrokes per cycle at 240 degrees of shaft 696 rotation, the fifthcylinder 610 may reach peak discharge pressure on a second of its twostrokes per cycle at 270 degrees of shaft 696 rotation, the thirdcylinder 606 may reach peak discharge pressure on a second of its twostrokes per cycle at 300 degrees of shaft 696 rotation, and the sixthcylinder 612 may reach peak discharge pressure on a second of its twostrokes per cycle at 330 degrees of shaft 696 rotation.

Accordingly, combining the pump 200 embodiment illustrated in FIG. 2with the partial system 600 embodiment illustrated in FIG. 6, where sixcylinders create 12 peak pressure points or pulsations per shaft 204rotation with each peak pressure point or pulsation occurring at 30degree intervals, fluid flowing from three cylinders 250, 252, and 254having six peak pressure points or pulsations occurring at 60 degreeintervals may be combined at a first junction (e.g., junction 660 inFIG. 6) and fluid flowing from three other cylinders 256, 258, and 260having six peak pressure points or pulsations occurring at 60 degreeintervals may be combined at a second junction (e.g., junction 662 inFIG. 6). By so combining fluid flow using equal length headers (e.g.,headers 642, 644, 646 and 648, 650, 652 in FIG. 6) pressure waves arecombined out of phase such that the pressure of the combined flowleaving the side junctions 660 and 662 has lower amplitude pressurewaves with lower pressure peaks or pulsations.

When flow from a first set of cylinders (first, second, and thirdcylinders 602, 604, and 606 in the embodiment depicted in FIG. 6) iscombined with flow from a second set of cylinders (fourth, fifth, andsixth cylinders 608, 610, and 612 in the embodiment depicted in FIG. 6)where pressure peaks or pulsations created by the first set of cylinders(first, second, and third cylinders 602, 604, and 606 in the embodimentdepicted in FIG. 6) are offset from pressure peaks or pulsations createdby the second set of cylinders (fourth, fifth, and sixth cylinders 608,610, and 612 in the embodiment depicted in FIG. 6) the headers 642, 644,646, 648, 650, and 652 may all be of equal length and the branch lines670 and 672 that combine the flow from the first set of cylinders andthe second set of cylinders

The embodiment illustrated in FIG. 6 is one example of combining fluidflow from cylinders at least some of which operate out of phase. Itshould be recognized, however, that various systems, methods, andapparatuses may be used to combine fluid flowing from multiple cylindersoperating in or out of phase to cancel or attenuate pressure waves orpulsations propagating through the fluid. Thus, any number of cylindersmay be combined out of phase in one or more sets of cylinders and anynumber of sets of cylinders may be combined out of phase by branchlines.

In the embodiment illustrated in FIG. 6, the pressure peaks or pulsescreated by the first set of cylinders 602, 604, and 606 areapproximately 180 degrees out of phase from the pressure peaks or pulsescreated by the second set of cylinders 608, 610, and 612. Accordingly,if the headers 642, 644, 646, 648, 650, and 652 connected to all sixcylinders 602, 604, 606, 608, 610, and 612 are of equal length and thebranch lines 670 and 672 connecting the flow from the first side 616 tothe flow from the second side 618 are of equal length, then the combinedpressure waves emanating from the first side junction 660 will be 180degrees out of phase with the combined pressure waves emanating from thesecond side junction 662 and the flows passing through the branch lines670 and 672 will combine at the branch junction 678 180 degrees out ofphase, thereby further reducing pressure waves or pulsations propagatingthrough the branch lines 670 and 672.

FIG. 7 illustrates a tuned loop network 700 that includes two tunedloops 702 and 752. Those two tuned loops 702 and 752 may each be similarto the tuned loop 102 illustrated in FIG. 1. Those two tuned loops 702and 752 may furthermore be incorporated into any portion of a fluidpumping system such as the fluid pumping system 440 illustrated in FIG.4 (e.g., in one or more headers 460, 462, 464, and 466, one or morebranch lines 470 and 472, or in place of or in addition to the tunedloop 480).

A fluid, such as a gas or liquid may be pumped through the tuned loopnetwork 700 by, for example, a pump, such as the pump 450 illustrated inFIG. 4, the pump 550 illustrated in FIG. 5, the pump 694 illustrated inFIG. 6, the pump 806 illustrated in FIG. 8, the pump 906 illustrated inFIG. 9, or any other pump described herein or other than as describedherein and the pump may be a reciprocating compressor. The lengths ofthe various conduits (e.g., 716, 722, 766, 772) may be adjusted tocancel primary pulsations and harmonics over a range of the pump (e.g.,450, 550, 694, 806, and 906) operating speeds or conditions.

The first tuned loop 702 illustrated in FIG. 7 includes an inlet conduit704 coupled to a first inlet junction 706. The first inlet junction 706includes an inlet 708, a first outlet 710 and a second outlet 713. Thefirst tuned loop 702 illustrated in FIG. 7 also includes a firstattenuating conduit 716 having a first end 714 coupled to the firstoutlet 710 of the inlet junction 706, having a first length, and havinga second end 718 opposite the first end 714.

The first tuned loop 702 illustrated in FIG. 7 also includes a secondattenuating conduit 722 having a first end 720 coupled to the secondoutlet 713 of the inlet junction 706, having a length that isapproximately equal to the length of the first attenuating conduit 716plus half a first primary wavelength of a pressure wave or pulsations orvibrations propagating in a fluid flowing through the tuned loop network700. The first primary wavelength may be selected from a range ofwavelengths that may be imparted on the fluid by the pump (e.g., 450,550, 694, 806, and 906).

The term “wavelength,” as used in this section, may indicate thedistance over which a wave's shape repeats, wherein the wave is formedby the repeating pressure variations or pulsations of the pump (e.g.,450, 550, 694, 806, and 906) which may be caused by the motion of apiston (e.g., 230, 232, 234, 236, 238, 240 330, 332, 334, 336, 338, and340 illustrated in FIGS. 2 and 3) in a cylinder (e.g., 452, 454, 456,458, 552, 554, 556, 558, 602, 604, 606, 608, 610, and 612 illustrated inFIGS. 4, 5, and 6) compressing a gaseous fluid. The term “wavelength,”as used in this section, may also indicate the distance betweenconsecutive corresponding points of a repeating wave, such as a pressureoscillation wave, wherein the corresponding points of the wave maycorrespond to one or more positions of the piston in the cylinder (e.g.,452, 454, 456, 458, 552, 554, 556, 558, 602, 604, 606, 608, 610, and 612illustrated in FIGS. 4, 5, and 6). That distance may furthermore bemeasured in length of pipe, such that the difference in length betweenthe first attenuating conduit 716 and the second attenuating conduit 722may be selected such that fluid flowing through those conduits iscombined at a first outlet 730 such that pressure waves or pulsations inthe fluid are attenuated.

The first tuned loop 702 illustrated in FIG. 7 further includes thefirst outlet junction 724 having a first inlet 726 coupled to the secondend 718 of the first attenuating conduit 716, a second inlet 734 coupledto the second end 728 of the second attenuating conduit 722, and anoutlet 730. The outlet 730 of the first outlet junction 724 may beattached to a discharge conduit 732 coupling the first tuned loop 702 tothe second tuned loop 752.

The second tuned loop 752 illustrated in FIG. 7 includes a second inletjunction 756 in fluid communication with the first outlet junction 724.The outlet junction 724 of the first tuned loop 702 may be coupleddirectly to the inlet junction 756 of the second tuned loop 752 withoutthe use of the connecting conduit 732 or the connecting conduit 732 mayinterconnect the outlet junction 724 to the inlet junction 756. Thesecond inlet junction 756 includes an inlet 758, a first outlet 760 anda second outlet 763. The second tuned loop 752 illustrated in FIG. 7also includes a third attenuating conduit 766 having a first end 764coupled to the first outlet 760 of the inlet junction 756, the thirdattenuating conduit 766 having a first length and having a second end768 opposite the first end 764.

The second tuned loop 752 illustrated in FIG. 7 also includes a fourthattenuating conduit 772 having a first end 770 coupled to the secondoutlet 763 of the second tuned loop 752 inlet junction 756, the fourthattenuating conduit 772 having a length that is approximately equal tothe length of the third attenuating conduit 766 plus half a secondprimary wavelength of pressure variations or vibrations propagating inthe fluid flowing through the tuned loop network 700, and having asecond end 778.

The second primary wavelength is also selected from a range ofwavelengths that may be imparted on the fluid by the pump (e.g., 450,550, 694, 806, and 906). The second primary wavelength will not be thesame as the first primary wavelength since the first tuned loop 702 andthe second tuned loop 752 are tuned to attenuate different wavelengthsin this embodiment. The second primary wavelength will also typicallynot be offset from the first primary wavelength by half the firstprimary wavelength since the purpose of the second tuned loop 752 inthis embodiment is not to cancel certain even harmonics of the firsttuned loop 702. Rather, the first and second tuned loops 702 and 752 arearranged to provide good attenuation over a range of pressure wave orpulsation frequencies that may be produced, for example, by adjustingthe speed of a pump (e.g., 450, 550, 694, 806, and 906).

The second tuned loop 752 illustrated in FIG. 7 further includes asecond outlet junction 774 having a first inlet 776 coupled to thesecond end 768 of the third attenuating conduit 766, a second inlet 784coupled to the second end 778 of the fourth attenuating conduit 772, andan outlet 780. The outlet 780 of the second outlet junction 774 may beattached to a system through which the fluid is being pumped through,for example, a system coupling conduit 782.

Each of the tuned loops 702 and 752 of the pulsation attenuation network700 may include two conduits 716, 722 or 766, 772, such as pipes ofapproximately equal area and different lengths, that extend from aheader 704 at a junction 706 or 756 and that are recombined at a pipe732 or 782 or vessel 786. When the areas of the two conduits 716, 722 or766, 772 are equal the two pressure waves or pulses carried therein canhave equal energy to effectuate attenuation of the pressure waves orpulses when the fluid flow carrying the pressure waves and pulses arerecombined.

In alternate embodiments, the conduits 716, 722 and 766, 772 of thetuned loops 702 and 752 may be of unequal cross-sectional size and thelengths of those conduits 716, 722 and 766, 772 may be varied by otherthan half of a wavelength of the pressure wave or pulse stream carriedin the fluid flowing through the conduits 716, 722 and 766, 772 to beattenuated, so as to effectuate pressure wave or pulsation attenuation.

Multiple tuned loops, such as the tuned loops 702 and 752 illustrated inFIG. 7 may be combined with the header cancellation system 460-478illustrated in FIG. 4. For example, tuned loops 702 and 752 may becoupled to branch line junction 478 in place of or in addition to thetuned loop 480 illustrated in FIG. 4. In another embodiment, one or moretuned loops, such as the tuned loops 702 and 752 illustrated in FIG. 7may be connected to the inlet (e.g., 804 and 904 as shown in FIGS. 8 and9) side of the pump (e.g., 450, 550, 694, 806, and 906), with or withoutadditional attenuation conduits, such as conduits 460, 462, 464, 466,468, 470, and 472 shown on the outlet (e.g., 808 and 908 as shown inFIGS. 8 and 9) side of the pump 450 illustrated in FIG. 4.

The inlet junctions (e.g., 706 and 756) may divide the fluid stream intotwo equal parts using two half-round or D-shaped ports that become roundand have a substantially constant area. A similarly configured outletjunction (e.g., 724 and 774) may be used to recombine the dividedstreams at the end of the tuned loop (e.g., 702 and 752).

Using the tuned loops of FIG. 7 as an example, wherein the variousconfigurations described in connection with FIG. 7 may be incorporatedinto various configurations including those illustrated and described inconnection with FIGS. 4, 5, 6, 8, and 9, the shorter of the two conduits716 and 766 in the tuned loops 702 and 752 may be of a selected lengthand the longer of the conduits 722 and 772 may be equal to the length ofthe shorter of the conduits 716 and 766 plus half of a wavelength ofpulsations, vibrations, or pressure waves propagating in the fluid of aprimary frequency to be canceled or attenuated.

FIG. 8 illustrates an embodiment of a tuned loop network 800 having afirst tuned loop 802 in fluid communication with the inlet 804 of a pump806 and a second tuned loop 852 in fluid communication with the outlet808 of the pump 806. In the embodiment illustrated in FIG. 8, the inlet804 may also be referred to as a suction side of the pump 806 and theoutlet 808 may also be referred to as a discharge side of the pump 806.Those tuned loops 802 and 852 may be configured as shown in FIG. 1, 4,or 7 and as described in connection with FIG. 1, 4, or 7. Either or bothof those tuned loops 802 and 852 may furthermore be used in connectionwith the piping system 440 illustrated and discussed in connection withFIG. 4, for example, or another piping system.

Pressure waves and pulsations generally exist in both the inlet 804 andoutlet 808 of a pump 806. Therefore, attenuating pressure waves andpulsations in both the inlet 804 and outlet 808 of the pump 806 byapplying at least one tuned loop 802 and 852 at each of the inlet 804and outlet 808 of the pump 806 may be beneficial to reduce pressurewaves and pulsations existing prior to the inlet 804 and propagatingfrom the outlet 808.

FIG. 9 illustrates yet another embodiment wherein a suction tuned loopnetwork 902 is placed at the suction 904 side of a pump 906 and adischarge tuned loop network 952 is placed at the discharge side 908 ofthe pump 906. The suction tuned loop network 902 may include any desirednumber of tuned loops such as, for example the two tuned loops 910 and912 illustrated in FIG. 9. Similarly, the discharge tuned loop network952 may include any desired number of tuned loops such as, for example,the two tuned loops 960 and 962 illustrated in FIG. 9. The suction tunedloop network 902 and discharge tuned loop network 952 may furthermore beconstructed as illustrated in and described in connection with FIGS. 1,4, 5, and 7.

It should be noted that the acoustic velocity of a gas being pumped mayvary from the inlet 904 to the outlet 908 of a pump 906 and, for atleast that reason, the tuned loop configurations on the inlet 904 sideand outlet 908 sides of the pump 906 may not be identical. It shouldalso be recognized that a tuned loop network of two or more tuned loops910, 912, and 960, 962 may be used on the inlet 904, the outlet 908, orboth the inlet 904 and the outlet 908 of the pump 906.

Simulations have shown that tuned loop networks having three tuned loopsare likely to provide substantial benefit over networks having two tunedloops in certain applications and that tuned loop networks having fourtuned loops are likely to provide substantial benefit over networkshaving three tuned loops in certain applications. Thus, it iscontemplated that three, four, or more tuned loops 910, 912, and 960,962 may be placed on either or each side of the pump 906 as required ordesired to attenuate pulsations, vibrations, or other waves present influid received at or discharged from the pump 906.

Other configurations having two or more tuned loops 910, 912 and 960,962 placed on one or both sides 904 and 908 of the pump 906 are alsopossible to attenuate one or more primary frequencies or an entire rangeof frequencies. As has been discussed, a range of frequencies may existwhere, for example, the speed of the pump 906 is varied.

Tuned loops networks such as those illustrated in FIG. 9 (902 and 952)can create relatively steady pressure upstream or downstream of the pump906 in comparison to the wide pressure variations that may exist influid flow created by the pump 906. When tuned loop networks (e.g., 902and 952) are properly positioned, the pump 906 may require less power tocreate a desired pressure downstream in a pipe or vessel, may provide agreater differential pressure created by the pump 906, or both.

Using FIG. 9 as an example, a wavelength may be determined using thespeed of the pump 906, the number of compression volumes (per rotationof the pump 906, for example), and the acoustic velocity of the fluidbeing pumped by the pump 906. Thus, a single-acting reciprocatingcompressor type pump 906 having a single cylinder may be used tocompress a gas and propel the gas through the inlet 904 once per enginecycle, as an example.

Pumps (e.g., 450, 550, 694, 806, and 906) including reciprocatingcompressors frequently operate over a range of speeds. In this example,a single acting reciprocating compressor 906 operates at 600 rpm, whichis equal to a primary frequency of 10 revolutions per second. A singlecompression occurs in each cylinder during each rotation of thissingle-acting reciprocating compressor 906. If the velocity of the gasis 1000 ft/sec., the gas moves 100 feet per revolution of thereciprocating compressor 906 and its half wavelength would be 50 feet.In a double-acting reciprocating compressor, which compresses the gasand propels the gas through the inlet 904 on both strokes, thewavelength is half the wavelength of a single-acting reciprocatingcompressor so that, in the example provided, half a wavelength would be25 feet.

In a two-stage pressure wave or pulsation attenuation network (e.g., thetuned loop network 700 illustrated in FIG. 7 or the suction tuned loopnetwork 902 or the discharge tuned loop network 952 illustrated in FIG.9), the first pressure wave or pulsation attenuation device 702, 912,and 962 in the series may be designed to eliminate the most prevalentprimary frequency expected to be present in the fluid passing throughthe pressure wave or pulsation attenuation network 700, 902, and 952.That primary frequency eliminating pulsation attenuation device 702,912, and 962 may furthermore be the longest of the pressure wave orpulsation attenuation devices 702, 752, 912, 910, 962, and 960 in theseries of pressure wave or pulsation attenuation devices 702, 752, 912,910, 962, and 960 placed in series to form the pulsation attenuationnetwork 700, 902, and 952.

FIG. 10 illustrates an embodiment of a method for attenuatingpulsations, vibrations, or other undesirable waves in a fluid 1000. Themethod for attenuating pulsations 1000 begins with a first wave, such asa pulse wave, entering a first pipe, duct, or conduit at 1010 and asecond wave, such as a pulse wave, entering a second pipe, duct, orconduit at 1020. Each of the first wave and the second wave willpropagate in a fluid, such as a liquid or gas, which is being pumped. At1030, the first wave and the second wave are combined, for example, byconducting the first and second waves into a junction coupled to firstand second branch conduits carrying fluid in which the first and secondwaves are propagating. The first and second waves may be attenuated bysuch a combination of waves where, for example, the waves are combinedat a time when a pulse peak in the first wave joins near a pulse valleyin the second wave.

To further attenuate pulses, vibrations, or other undesirable waves in afluid, at 1040 the fluid that was combined at 1030 may be combined withanother fluid in such a way as to attenuate waves existing in thecombined fluid and the other fluid.

Such combinations of fluid as described at 1030 and 1040, wherein wavespropagating in the fluid are combined out of phase, may result in adifferential phase shift in the combined fluids, thereby attenuating thepulsations, vibrations, and other undesirable waves.

For example, in the method illustrated and described in connection withFIG. 10, fluid flows from two or more cylinders (e.g., 460, 462, 464,466, 560, 562, 564, 566, 602, 604, 606, 608, 610, and 612) are combinedat a junction (e.g., 474, 476, 574, 576, 660, and 662) to reducevariations or fluctuations in pressure waves propagating from thosecylinders (e.g., 460, 462, 464, 466, 560, 562, 564, 566, 602, 604, 606,608, 610, and 612) at 1030. The fluid flowing from the cylinders (e.g.,460, 462, 464, 466, 560, 562, 564, 566, 602, 604, 606, 608, 610, and612) is combined such that pressure waves caused by operation of thecylinders (e.g., 460, 462, 464, 466, 560, 562, 564, 566, 602, 604, 606,608, 610, and 612) join out of phase at 1030. In one embodiment, theflows are a gaseous fluid, such as natural gas. In an embodiment,periodic pressure waves exist in the flow propagating from each cylinder(e.g., 460, 462, 464, 466, 560, 562, 564, 566, 602, 604, 606, 608, 610,and 612) and the flows from two cylinders (e.g., 460, 462, 464, 466,560, 562, 564, 566, 602, 604, 606, 608, 610, and 612) are combined 180degrees out of phase at 1030. In another embodiment, the flowspropagating from three or more cylinders are combined at 1030 such thatpressure peaks or pulsations in the flows arrive at the place where theflows are combined at regular intervals, such as 60 degrees out of phasewhen combining flow from three cylinders (e.g., 602, 604, and 606 or608, 610, and 612) or 45 degrees out of phase when combining flow fromfour cylinders.

The pressure waves in the fluid streams combined at 1030 may not besymmetrical such that a first wave near its peak pressure may be joinedwith a second wave near its low pressure so as to attenuate both waves,but not necessarily cancel both waves.

At 1040, a further reduction in the amplitude of pressure waves may beachieved by combining two or more flows of fluid that carry combinedflows from two or more headers (for example, flow from side junctions474, 476, 574, 576, 660, and 662) out of phase in a branch line junctionfor example, branch line junction 478, 578, or 678. In an embodiment,the combined header flows may be combined directly by, for example,connecting side junctions 660 and 662 directly in another junction suchas branch line junction 678 without the use of branch lines 670 and 672.In another embodiment, as illustrated in FIGS. 4 and 6, combined headerflow may be combined at side junctions (e.g., 474, 476 and 660, 662) andbranch lines (e.g., 470, 472, 670, and 672) may carry flow from the sidejunctions (e.g., 474, 476 and 660, 662) to the branch line junction(e.g., 478 and 678).

Cylinders (e.g., 452, 454, 456, 458, 552, 554, 556, 558, 602, 604, 606,608, 610, and 612) may be of varying capacity such that flows from thecylinders may be combined out of phase at intervals other than 360degrees divided by the number of cylinders being combined. Moreover, thetotal flow traveling along two or more branch lines (e.g., 470, 472,570, 572, 670, and 672) that are to be combined may vary, for example,in quantity or amplitude of pressure waves, such that flows through thebranch lines may be combined out of phase at intervals other than 360degrees divided by the number of branch lines to be combined.

In accordance with one embodiment of pressure wave or pulsationattenuation, and depicted in the flow chart of FIG. 11, a method ofattenuating pressure waves or pulsations created by a pump 1100includes: discharging a first fluid stream from a first cylinder into afirst conduit at 1112, discharging a second fluid stream from a secondcylinder into a second conduit at 1114, discharging a third fluid streamfrom a third cylinder into a third conduit at 1116, discharging a fourthfluid stream from a fourth cylinder into a fourth conduit at 1122,discharging a fifth fluid stream from a fifth cylinder into a fifthconduit at 1124, discharging a sixth fluid stream from a sixth cylinderinto a sixth conduit 1126, the first, second, third, fourth, fifth, andsixth conduits having equal lengths, and the pressure waves in thefirst, second, third, fourth, fifth, and sixth fluid streams havingrelative phases that vary by approximately 60 degrees at the points ofdischarge from the first, second, third, fourth, fifth, and sixthcylinders respectively.

In an embodiment, the fluid streams from the first, second, and thirdconduits are combined at 1130 and the fluid streams from the fourth,fifth, and sixth conduits are combined at 1140. Such a combination mayoccur to minimize the lengths of the conduits when, for example, a firstset of cylinders are in close proximity to one another (for example, onone side of a compressor) while a second set of cylinders are close toone another, but further from the first set of cylinders. In that wayproximate flows can be joined and used to reduce pressure waves orpulsations quickly and close to the cylinders. The flows may furthermorebe joined in one or more junctions such as side junctions 474, 476, 574,576, 660, and 662.

Further in that embodiment, the fluid streams discharged from the first,second and third conduits may be directed into a seventh conduit of asecond length at 1130 and the fluid streams discharged from the fourth,fifth and sixth conduits may be directed into an eighth conduit of alength equal to the second length at 1140. The gas discharged from theseventh and eighth conduits is then combined at 1150 and thatcombination may occur in a branch line junction such as one of branchline junctions 478, 578, and 678.

In various embodiments, the first and second lengths may be chosen tooptimize or improve flow or power consumption or to improve both flowand power consumption.

FIG. 12 illustrates a fluid pumping system 1210, such as may be used ina natural gas pumping application. The fluid pumping system 1210 has asuction side 1222 and a discharge side 1224. Fluid is supplied to thesuction side 1222 of the pump 1216 from a source system 1212, such asanother pumping station in a natural gas pumping system. The fluidsupplied to the pump 1216 passes through one or more suction side tunedloops 1214, such as the tuned loop 100 illustrated in FIG. 1 or thetuned loops 702 and 752 illustrated in FIG. 7 before reaching the pump1216. The first pipe 1232 carries fluid from the source 1212 to thesuction side tuned loop 1214 and the second pipe 1234 carries fluid fromthe suction side tuned loop 1214 to the pump 1216.

The fluid discharged from the pump 1216 also passes through one or moredischarge side tuned loops 1218 (such as the tuned loop 100 illustratedin FIG. 1 or the tuned loops 702 and 752 illustrated in FIG. 7) afterbeing discharged from the pump 1216 and before reaching its destination.That destination may, for example, be a home or another pumping stationin a natural gas pumping system. Third pipe 1236 carries fluid from thepump 1216 to the discharge side tuned loop 1218 and fourth pipe 1238carries fluid from the discharge side tuned loop 1218 to the destination1220.

It should be recognized that the fluid pumping system 1210 illustratedin FIG. 12 is simple and that many more components may be situatedbetween the source 1212 and the pump 1216 or between the pump 1216 andthe destination 1220.

A first consideration in designing a tuned loop 1214 or 1218 may be toselect appropriate dimensions for the first branch line (e.g., firstbranch line 116 illustrated in FIG. 1) and the second branch line (e.g.,second branch line 122 illustrated in FIG. 1) to attenuate pulsations orpressure waves emanating from the pump 1216.

A second consideration in designing a tuned loop 1214 or 1218 may be toselect appropriate length and area dimensions for the pipes 1232, 1234,1236, and 1238. For example, the dimension of second pipe 1234 may beselected such that waves reflected from the suction side tuned loop 1214back upstream toward the pump 1216 reach the pump 1216 at a time in thepump 1216 operation that causes the pump 1216 to be more efficient, tocreate more flow, or a combination of both. The dimension of third pipe1236 may also be selected such that waves reflected from the dischargeside tuned loop 1218 back toward the pump 1216 reach the pump 1216 at atime in the pump 1216 operation that causes the pump 1216 to be moreefficient, to create more flow, or a combination of both.

Thus, the location of a pressure wave or pulsation attenuation network(e.g., 100, 440, 540, 600, 700, 800, and 900), components thereof, oranother source of reflected waves in relation to the pump (e.g., 450,550, 694, 806, and 906) or another source of pulsations, vibrations, orwaves in fluid flowing through a system (e.g., 100, 440, 540, 600, 700,800, and 900) may affect the quantity or efficiency of flow through thesystem (e.g., 100, 440, 540, 600, 700, 800, and 900). In an embodimentwhere the source of the pulsation is a reciprocating compressor (e.g.,450, 550, 694, 806, and 906) pumping natural gas through a natural gaspiping system (e.g., 100, 440, 540, 600, 700, 800, and 900), a headerpipe (e.g., headers 460, 462, 464, 466, 560, 562, 564, 566, 642, 644,646, 648, 650, and 652 in FIGS. 4, 5, and 6) may be employed to carrythe compressed gas from the compressor (e.g., 450, 550, 694, 806, and906) to the system (e.g., 100, 440, 540, 600, 700, 800, and 900) andthat header (e.g., headers 460, 462, 464, 466, 560, 562, 564, 566, 642,644, 646, 648, 650, and 652) may have a particular length that maypromote quantity or efficiency of fluid flow through the system (e.g.,100, 440, 540, 600, 700, 800, and 900).

Lengths and areas of piping on the intake side of the pump (e.g., 450,550, 694, 806, and 906) or other source of pulsations, vibrations, orwaves in fluid flowing through a system (e.g., 100, 440, 540, 600, 700,800, and 900) may affect the efficiency of flow through the system(e.g., 100, 440, 540, 600, 700, 800, and 900) as well. In an embodimentwhere the source of a pressure wave that includes pressure peaks orpulsations is a reciprocating compressor (e.g., 450, 550, 694, 806, and906) pumping natural gas through a natural gas piping system (e.g., 100,440, 540, 600, 700, 800, and 900), an intake pipe (e.g., 590) may beemployed to carry the compressed gas from the tuned loop (e.g., 100 and580) to the compressor (e.g., 450, 550, 694, 806, and 906). That intakepipe (e.g., 590) may furthermore have a particular length that maypromote quantity or efficiency of fluid flow through the system (e.g.,100, 440, 540, 600, 700, 800, and 900).

While the present invention has been disclosed with reference to certainembodiments, numerous modifications, alterations, and changes to thedescribed embodiments are possible without departing from the scope ofthe present invention, as defined in the appended claims. Accordingly,it is intended that the present invention not be limited to thedescribed embodiments, but that it have the full scope defined by thelanguage of the following claims, and equivalents thereof.

1. A natural gas pumping system, comprising: a reciprocating compressorincluding: a first cylinder having: an inlet through which natural gasis received; and an outlet through which natural gas is discharged; asecond cylinder having: an inlet through which natural gas is received;and an outlet through which natural gas is discharged; a first conduithaving a first end in fluid communication with the outlet of the firstcylinder and a second end in fluid communication with a junction; and asecond conduit having a first end in fluid communication with the outletof the second cylinder and a second end in fluid communication with thejunction.
 2. The natural gas compressor of claim 1, wherein the firstend of the first conduit is connected to the outlet of the firstcylinder and the second end of the second conduit is connected to theoutlet of the second cylinder.
 3. The natural gas compressor of claim 1,wherein the junction is not a tank.
 4. The natural gas compressor ofclaim 1, wherein the junction is not a bottle.
 5. The natural gascompressor of claim 1, wherein the first conduit has a firstcross-sectional area, the second conduit has a second cross-sectionalarea, and the junction has an outlet having a third cross-sectional areanot more than two times the first cross-sectional area and the secondcross-sectional area combined.
 6. The natural gas compressor of claim 5,further comprising an outlet conduit coupled to the junction outlet. 7.A natural gas pumping system, comprising: a reciprocating compressorincluding: a first cylinder having: an inlet through which natural gasis received; and an outlet through which natural gas is discharged; asecond cylinder having: an inlet through which natural gas is received;and an outlet through which natural gas is discharged; a first conduithaving a first end in fluid communication with the inlet of the firstcylinder and a second end in fluid communication with a junction; and asecond conduit having a first end in fluid communication with the inletof the second cylinder and a second end in fluid communication with thejunction.
 8. The natural gas compressor of claim 7, wherein the firstend of the first conduit is connected to the inlet of the first cylinderand the second end of the second conduit is connected to the inlet ofthe second cylinder.
 9. The natural gas compressor of claim 7, whereinthe first conduit has a first cross-sectional area, the second conduithas a second cross-sectional area, and the junction has an outlet havinga third cross-sectional area not more than two times the firstcross-sectional area and the second cross-sectional area combined. 10.The natural gas compressor of claim 9, further comprising an inletconduit coupled to the junction outlet.
 11. A method of reducingpressure variations in a natural gas pumping system, the methodcomprising: combining natural gas flowing from a first reciprocatingcylinder having a first periodic pressure fluctuation characteristicoperating in a first phase with natural gas flowing from a secondreciprocating cylinder having a second periodic pressure fluctuationcharacteristic operating in a second phase when the first periodicpressure fluctuation characteristic is out of phase with the secondperiodic pressure fluctuation characteristic.
 12. The method of claim11, wherein the natural gas flowing from the first reciprocatingcylinder is combined with natural gas flowing from the secondreciprocating cylinder at a junction.
 13. A pressure wave attenuationsystem, comprising: one or more reciprocating compressors togethercomprising a first cylinder, a second cylinder, and a third cylinder; afirst header coupled to the first cylinder and a first junction; asecond header coupled to the second cylinder and the first junction suchthat a pressure wave propagating in the fluid flowing through the firstheader is out of phase with fluid flowing through the second header whenthe fluid flowing from the first and second headers combine at the firstjunction; a third header coupled to the third cylinder and a secondjunction; and a first branch line extending from the first junction tothe second junction.
 14. A pressure wave attenuation system, comprising:one or more reciprocating compressors together comprising a firstcylinder, a second cylinder, a third cylinder, and a fourth cylinder; afirst header in fluid communication with the first cylinder and a firstjunction; a second header in fluid communication with the secondcylinder and the first junction such that a pressure wave propagating inthe fluid flowing through the first header and a pressure wavepropagating in the fluid flowing through the second header areattenuated when the fluid flowing from the first header and the fluidflowing through the second header combine at the first junction; a thirdheader in fluid communication with the third cylinder and a secondjunction; a fourth header in fluid communication with the fourthcylinder and the second junction such that a pressure wave propagatingin the fluid flowing through the third header and a pressure wavepropagating in the fluid flowing through the fourth header areattenuated when the fluid flowing from the third header and the fluidflowing through the fourth header combine at the second junction; afirst branch line in fluid communication with the first junction and athird junction; and a second branch line in fluid communication with thesecond junction and the third junction, the length of the second branchline differing from the length of the first branch line such that apressure wave propagating in the fluid in the first branch line and apressure wave propagating in the fluid in the second branch line areattenuated when the fluid flows from the first and second branch linescombine at the third junction.
 15. The pressure wave attenuation systemof claim 14, wherein: the pressure wave propagating in the fluid flowingthrough the first header is out of phase with the pressure wavepropagating in the fluid flowing through the second header when thefluid flowing from the first header and the fluid flowing through thesecond header combine at the first junction; the pressure wavepropagating in the fluid flowing through the third header is out ofphase with the pressure wave propagating in the fluid flowing throughthe fourth header when the fluid flowing from the third header and thefluid flowing through the fourth header combine at the first junction;and the pressure wave propagating in the fluid flowing through the firstbranch line is out of phase with the pressure wave propagating in thefluid flowing through the second branch line when the fluid flowing fromthe first branch line and the fluid flowing through the second branchline combine at the third junction.
 16. The pressure wave attenuationsystem of claim 15, wherein the lengths of the first and second headerscause the pressure waves in the fluid flowing through the first andsecond headers to be out of phase.
 17. The pressure wave attenuationsystem of claim 14, wherein the length of the second header differs fromthe length of the first header such that the pressure wave in the firstheader and the pressure wave in the second header are attenuated whenthe fluid flowing from the first and second headers combine at the firstjunction.
 18. The pressure wave attenuation system of claim 17, whereinthe length of the fourth header differs from the length of the thirdheader such that the pressure wave in the fourth header and the pressurewave in the third header are attenuated when the fluid flowing from thethird and fourth headers combine at the second junction.
 19. Thepressure wave attenuation system of claim 14, wherein the length of thefirst header is the same as the length of the second header.
 20. Thepressure wave attenuation system of claim 14, wherein the length of thethird header is the same as the length of the fourth header.
 21. Thepressure wave attenuation system of claim 14, wherein: the first headeris coupled to an outlet of the first cylinder and the first junction;the second header is coupled to an outlet of the second cylinder and thefirst junction; the third header is coupled to an outlet of the thirdcylinder and the second junction; the fourth header is coupled to anoutlet of the fourth cylinder and the second junction; the first branchline is coupled to the first junction and the third junction; and thesecond branch line is coupled to the second junction and the thirdjunction.
 22. The pressure wave attenuation system of claim 14, furthercomprising: a fifth cylinder and a sixth cylinder of the one or morecompressors; a fifth header in fluid communication with the fifthcylinder and the first junction carrying a fluid having a pressure wavepropagating therein such that the pressure waves propagating in thefluid flowing through the first header, second header, and fifth headerare attenuated when the fluid flowing from the first header, secondheader, and fifth header combine at the first junction; a sixth headerin fluid communication with the sixth cylinder and the second junctioncarrying a fluid having a pressure wave propagating therein such thatthe pressure wave propagating in the fluid flowing through the thirdheader, fourth header, and sixth header are attenuated when the fluidflowing from the third header, fourth header, and sixth header combineat the second junction.
 23. A method of attenuating pressure waves in anatural gas pumping system, comprising combining gas flowing from afirst cylinder in which propagates a first periodic wave with gasflowing from a second cylinder in which propagates a second periodicwave such that the first periodic wave and the second periodic wave areout of phase.
 24. The method of claim 23, wherein the cylinders operateout of phase.
 25. The method of claim 23, wherein the cylindersdischarge into different length conduits and the conduits are joined ata junction.
 26. The method of claim 23, wherein the gas is natural gas.27. The method of claim 23, wherein the first cylinder includes a firstpiston reciprocating within the cylinder and the second cylinderincludes a second piston reciprocating within the cylinder.
 28. Themethod of claim 27, wherein the first and second pistons compress gas oneach of two strokes within the cylinder.